To identify microRNAs (miRNAs) responsive to powdery mildew (PM) infection and elucidate their regulatory roles in melon PM resistance, thereby laying a foundation for deciphering the underlying molecular mechanisms, we combined high-throughput sequencing with bioinformatics analysis to screen PM-responsive miRNAs and their target genes using PM-resistant and PM-susceptible melon genotypes. In total, 113 non-redundant miRNAs were identified in both genotypes, including 70 known and 43 novel miRNAs. Subsequent differential expression analysis revealed distinct miRNA responses to PM infection between resistant and susceptible genotypes. Upon PM inoculation, 13 miRNAs showed significant differential expression in both susceptible and resistant genotypes. In addition, four miRNAs, including miR164c, miR396a, miR398a and miRn39, displayed differential expression specifically in the susceptible genotype. Conversely, five miRNAs (miR167c, miR398b, miR399g, miR530a and miRn8) showed differential expression exclusively in the resistant genotype upon PM infection. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses demonstrated that these miRNAs mediate melon’s susceptibility or resistance to PM by modulating plant immune homeostasis, antioxidant metabolism, and pathogen-triggered cell death. Quantitative real-time PCR (qRT-PCR) validation confirmed a negative regulatory relationship between the expression of PM-responsive miRNAs and their predicted target genes. Collectively, our findings provide novel insights and candidate targets for further investigations into miRNA functions and regulatory mechanisms underlying melon PM resistance.
The current challenges associated with the conservation and restoration of plant biodiversity make it necessary to test new biotechnological approaches. Optimizing the stages of clonal micropropagation using synthetic growth biostimulants—protatranes (1,2,3)—enables the targeted modification of physiological processes in plants. This increases their stress resistance, stimulates development, and reduces the cost of the final product. In this paper, the stimulating effect of the protatran (1), which we have named “crezacin”, on the processes of in vitro rooting and acclimatization to ex vitro conditions in microplants of the rare wild species Lilium pensylvanicum Ker Gawl was studied. No effect of crezacin and α-naphthylacetic acid on the development and growth of the microbulb during the rooting stage was detected. Crezacin at a concentration of 1.0 mg/L inhibited root elongation, but did not affect root number. Using α-naphthylacetic acid at a concentration of 0.93 mg/L was ineffective in inducing in vitro rhizogenesis. The survival rate of regenerated plants cultivated on media supplemented with crezacin was found to be 100%. The positive effect of crezacin on the content of photosynthetic pigments in the leaves of regenerated plants was also demonstrated. The addition of ultra-low concentrations (0.001–0.1 mg/L) of crezacin increased pigment content by up to 1.5 times (p < 0.05) compared to the control group. The increase in chlorophyll and carotenoid levels upon the addition of crezacin to the culture medium significantly facilitated the transition from a heterotrophic to an autotrophic mode of nutrition when microplants were transplanted into a soil substrate. Further research on clonal micropropagation of rare plant species and horticultural crops will be conducted using protatranes 2 and 3.
Rhododendron decorum Franch. has high ornamental value and emerging edible potential, but conventional propagation cannot meet the demand for high-quality, genetically uniform planting stock. This study optimized explant disinfection, adventitious bud induction, shoot proliferation, and rooting culture using stem segments and leaves from a winter-flowering naturally mutated individual of Rhododendron decorum, aiming to minimize contamination and browning. Results demonstrated that combined disinfection with 1% KMnO4 (10 min) and 10% H2O2 (4 min) outperformed single-treatment with 0.1% HgCl2. For primary culture, the optimal medium for adventitious bud induction was WPM + 30 g·L−1 sucrose + 7.5 g·L−1 agar + 0.56 g·L−1 Ca(NO3)2 + 100 mg·L−1 VC + 3 mg·L−1 TDZ + 0.1 mg·L−1 NAA, achieving an induction rate of 66.67%. During subculture, when the concentrations of TDZ and NAA were adjusted to 0.6 mg·L−1 and 0.05 mg·L−1, respectively, and 2 mg·L−1 GA3 was supplemented, stem nodes exhibited slight thickening but no significant shoot elongation. For rooting, the basal medium WPM + 20 g·L−1 sucrose + 7.5 g·L−1 agar + 0.56 g·L−1 Ca(NO3)2 + 100 mg·L−1 VC + 1 g·L−1 activated charcoal supplemented with 0.8 mg·L−1 NAA yielded superior rooting performance. Adding 2 mg·L−1 2iP tended to enhance rooting rate relative to the NAA-only treatment from an independent rooting experiment. For callus-mediated bud induction from leaves, 0.1 mg·L−1 TDZ + 0.01 mg·L−1 NAA was optimal. Notched fully expanded apical leaves from tissue-cultured plantlets showed highest adventitious bud induction under 0.3 mg·L−1 TDZ + 0.01 mg·L−1 NAA. The established micropropagation system supports bud sport variety selection, mass seedling production, and genetic transformation research.
Balancing the vegetative and reproductive developmental cycles in a citrus orchard is essential to maintain sustainability. Plant growth regulators (PGRs) offer an effective tool for managing shoot growth rate and fruit production of citrus trees. By moderating shoot elongation and reducing canopy expansion, PGRs help minimise the frequency and intensity of pruning, substantially reducing labour costs and improving orchard management. Evidence from multi-year experiments showed PGR-treated citrus trees can maintain or increase yield efficiency, producing equal or greater fruit/canopy (m3) than untreated controls. Strategic application of PGRs can moderate alternate bearing by promoting more consistent and fruitful shoots, stabilising annual yields. Economic assessments showed significant reductions in labour costs, especially when trees treated with PGRs required less hand pruning. This review synthesises historic and contemporary research and the mechanisms by which PGRs exert their effects in citrus. It identifies knowledge gaps, such as the need for long-term studies, optimal timing for different cultivars, and integrated strategies suited to different environmental conditions. Plant growth regulators could be an effective tool for stable citrus production, offering the potential for more efficient tree canopy management when used responsibly in accordance with regulatory requirements and integrated with other orchard management practices.
This study compared four sweet cherry cultivars—Regina, Sweetheart, Kordia and 0900 Ziraat—at two sites of contrasting altitude in Eskişehir province, Türkiye: Eskişehir (792 m) and Sarıcakaya (220 m). Across two growing seasons (2016–2017; n = 64), phenological stages were recorded and fruit were assessed for eighteen pomological traits and three phytochemical measures—total phenolic content (TPC), total flavonoid content (TFC) and DPPH radical scavenging activity. Location affected almost every pomological trait measured: fruit from the cooler Eskişehir site were heavier and more intensely red, whereas fruit from the warmer Sarıcakaya site had higher soluble solids content and acidity, and reached bud break and bloom roughly 13 days earlier. TPC, TFC and DPPH activity were all higher at Eskişehir than at Sarıcakaya (TPC: 1071.0 vs. 823.3 mg GAE kg−1 FW; TFC: 344.3 vs. 234.6 mg CE kg−1 FW; DPPH: 45.5% vs. 22.5% inhibition; p < 0.001). Kordia stood out with the highest antioxidant activity and was also among the cultivars richest in phenolics and flavonoids. TPC and TFC were strongly correlated (r = 0.93), and both tracked with skin redness and lower titratable acidity. Overall, growing location, rather than cultivar, was the strongest factor behind the pomological, phenological and phytochemical differences observed over the two study years.
Investigating genetic diversity is a prerequisite for the management and utilization of germplasm resources. This study assessed the genetic diversity and population structure of 103 olive (Olea europaea) varieties in the Liangshan region, Sichuan Province, China, based on fruit phenotypic traits and 48 simple sequence repeat (SSR) markers. There were high positive correlations between various fruit phenotypic indicators, while a few indicators showed negative correlations (e.g., stone longitudinal diameter was significantly negatively correlated with the fruit shape index and kernel shape index). Fresh fruit oil content was significantly negatively correlated with fruit longitudinal diameter, stone transverse diameter, stone longitudinal diameter, and fruit volume. The number of allelic variations at SSR loci in the population ranged from 2 to 22, with an average of 10.7. The mean Shannon’s information index (I), observed heterozygosity (Ho), and expected heterozygosity (He) of the 103 varieties were 1.529, 0.54, and 0.685, respectively, indicating relatively high genetic diversity between these olive varieties. Structure analysis, PCA, and PCoA consistently classified the varieties into two ancestral populations, with mean fixation index (FST) = 0.052 and gene flow (Nm) = 4.544, suggesting moderate genetic differentiation and extensive gene flow between the populations. Based on phenotypic clustering and phylogenetic analysis, eight varieties exhibiting synonymy or homonymy were successfully identified. Furthermore, molecular fingerprint profiles were established using seven pairs of SSR primers, which could effectively identify all varieties. This study provides a valuable reference for the management and breeding of olive germplasm resources in the Liangshan region.
Melon (Cucumis melo L.) is a globally significant horticultural crop whose fruit quality and postharvest shelf life are profoundly influenced by oxidative stress. Abscisic acid (ABA)-responsive element binding factors (ABFs), which represent the Group A subfamily of the basic leucine zipper (bZIP) transcription factor family, serve as pivotal components in the ABA signaling pathway. These factors play essential roles in regulating plant responses to abiotic stress as well as fruit development and maturation processes. In this study, a total of nine CmABF gene family members (CmABF1–CmABF9) were successfully identified within the melon genome using genome-wide identification techniques. Bioinformatic analysis indicated that all CmABF proteins contain a conserved bZIP domain. Physicochemical property analysis revealed that most of these proteins are unstable hydrophilic proteins and all are localized to the cell nucleus. Phylogenetic analysis categorized the CmABF family into three distinct evolutionary branches (Groups A, B, and C), exhibiting high conservation with homologous genes in Arabidopsis thaliana, Solanum tuberosum, and other species. Promoter analysis demonstrated that CmABF genes are rich in hormone-responsive elements (such as abscisic acid-responsive element (ABRE) and gibberellin-responsive element (GARE)) and stress-responsive elements (such as MYB binding sites (MBS) and anaerobic-response element (ARE)). To investigate their responses to oxidative stress and ABA signaling, we analyzed the expression patterns of these genes in melon fruit at 0, 7, 14, 21, 28, and 35 days of postharvest storage under ozone (O3, an oxidative stressor), exogenous abscisic acid (ABA), and the ABA synthesis inhibitor nordihydroguaiaretic acid (NDGA) using RNA-seq and qRT-PCR. The results showed that ozone treatment significantly induced the up-regulation of CmABF9 while inhibiting the early expression of CmABF2 and CmABF4. ABA treatment generally promoted the transcription of family members during the late stages of storage (35 d). NDGA treatment suppressed the expression of CmABF2 and CmABF4 during the early storage stage (7 d), while markedly increasing their expression levels at later storage stages (28 d and 35 d), suggesting a compensatory feedback response under endogenous ABA deficiency. Furthermore, protein–protein interaction predictions indicated potential close interactions between CmABF proteins and SnRK2 protein kinases. This study provides a theoretical basis for elucidating the molecular mechanisms of the CmABF family in regulating postharvest oxidative stress in melon and provides candidate gene resources for molecular breeding aimed at enhancing resistance and extending the shelf life of melon fruit.
With the intention of investigating in further depth the horticultural biodiversity resulting from the selection and conservation effort carried out by farmers (custodians) who are dedicated to growing traditional products, we focused on six local landraces of Brassica rapa L. subsp. sylvestris (L.) Janch.; we conducted analyses addressing the presence of glucosinolates (GLSs), phenolic compounds and the antioxidant capacity of extracts of B. rapa landraces belonging to three groups with different growth phase behavior from planting to inflorescence appearance in the Salento area (Puglia or Apulia region, Italy). The studies focused on three local landraces known by Salento farmers as cima di rapa cinquantina (two separate accessions, 50SC and 50SD), cima di rapa sessantina (accessions 60SC and 60SD) and rapacaula (accessions rcSD and rcGA). We revealed the presence of eleven different glucosinolates and three main flavonoids, such as kaempferol, quercetin and isorhamnetin derivatives. The distribution and content of glucosinolates and flavonoids varied widely among the different landraces. Glucobrassicanapin was the predominant compound in all landraces, followed by gluconapin, except for 60SC, where the main GLS was the indolic glucobrassicin. Moreover, 50SC, 50SD and 60SC are characterized by the highest flavonoid content and the highest antioxidant capacity. The findings provide the basis for the characterization of B. rapa subsp. sylvestris L. local landraces as a useful source of valuable metabolites for human health, as well as for identifying one landrace with higher nutritional value as a starting point for accession conservation and economic development.
Fruit-tree pruning has to keep tree structure under control while continually renewing fruiting wood, and many decisions still depend on practical experience. This narrative review synthesizes 92 English-language publications from 1983 to 2026, identified through Google Scholar and backward citation tracking. As orchard systems become more regular and mechanization expands, mechanical pruning has been used to control canopy edges. Vision and 3D sensing are now being used to identify branches and locate pruning points, while robotic systems are beginning to attempt selective pruning. This review looks at the literature at canopy and branch scales. Mechanical canopy pruning is effective for quickly treating regular canopy profiles, but field trials show that regrowth, follow-up manual pruning, and crop-load management can change later yield and economic outcomes. Branch-level automation has moved from 2D recognition to 3D reconstruction, pruning-point generation, and small-scale robotic trials. The harder questions are increasingly about branch function and continuous whole-tree operation. For pruning automation, machine speed or a successful cut is only part of the result; post-pruning tree responses and longer-term production also have to be considered. Multi-temporal tree records, branch-function information, continuous operation, and long-term field testing deserve more attention.
Chromatin accessibility is an important feature of cis-regulatory elements that shapes gene regulation in plants; however, it has been studied less frequently in traditional medicinal plants such as Gardenia jasminoides J.Ellis (G. jasminoides). This study applied Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) technology to characterize the genome-wide distribution and functional features of accessible chromatin regions (ACRs) in G. jasminoides leaves. A total of 26,461 ACRs and 13,625 associated genes were identified in this study, and our results revealed a positive correlation between the open chromatin state of ACRs and the expression levels of their associated genes. These ACRs were also found to be enriched with numerous conserved transcription factor binding motifs (TF motifs). Integration of two histone modification datasets further demonstrated that ACRs are closely associated with activating histone modifications, including H3K4me3 and H3K27ac, which work together to regulate the transcription of target genes. Additionally, luciferase (LUC) reporter assays validated the transcriptional activation activity of two candidate ACRs. Taken together, these findings elucidate the genomic features of ACRs in G. jasminoides and provide critical genomic resources for subsequent gene regulation analyses for this species.
Plant tissue and cell culture techniques have proven to be a suitable tool for increasing fresh biomass and stimulating the plant secondary metabolite biosynthesis, offering important advantages compared to conventional plant propagation. Medicinal and aromatic plants represent species of interest due to their rich content in bioactive compounds, with various applications in different fields, including the food industry. The micropropagation technique, through the production of a large number of in vitro plants, can ensure, in a short time and with high efficiency, the adequate amount of fresh biomass to cover the need for the extraction of significant active principles for their use in the food industry as natural preservatives and antioxidants, as well as coloring and flavoring agents. This narrative review aims to provide a comprehensive analysis of the strategic micropropagation methods applied to medicinal and aromatic plants, including sustainable approaches (e.g., organic nutrient supplementation of the culture medium), as well as their advantages and limitations. Moreover, this bibliographical study highlights the role of the in vitro multiplication technique in enhancing the accumulation of secondary metabolites such as phenolics, flavonoids, alkaloids, terpenoids, saponins, etc., supporting their use for a more sustainable future in food systems. Finally, the present analysis points towards emerging future directions for exploiting the micropropagation technique on a large scale as a valuable and promising tool to reach its full potential as a source of novel biomolecules. This comprehensive integration serves as a valuable reference for researchers and industry experts in both plant biotechnology and food science and technology.
Grafting is the primary vegetative propagation technique for ornamental crabapple, and rootstock–scion compatibility critically determines graft healing efficiency and seedling quality. Selecting suitable rootstocks is essential for the popularization of new crabapple cultivars, yet the healing performance of the newly bred cultivar Malus ‘Huabiao’ grafted onto different local Malus rootstocks remains unclear. This study evaluated graft compatibility for M. ‘Huabiao’ grafted onto three rootstocks (M. hupehensis, M. robusta, and M. baccata) through histological observation and dynamic detection of soluble sugar, soluble protein, and tannin during graft healing. The results indicated that M. ‘Huabiao’/M. hupehensis and M. ‘Huabiao’/M. robusta achieved higher survival rates (80.0% and 83.3%, respectively) and complete vascular reconstruction within 28 days, whereas the M. ‘Huabiao’/M. baccata combination exhibited a lower survival rate (63.0%) and obvious healing lag. All combinations showed consistent physiological variation trends, while the M. baccata group maintained higher soluble sugar content, greater protein fluctuations, and significantly elevated tannin levels (p < 0.05). Physiological substance accumulation was closely correlated with healing performance, with higher soluble sugar and protein levels associated with better wound recovery, and excessive tannin accumulation correlated with retarded tissue regeneration capacity. Distinct healing asynchrony was observed among combinations, with incomplete vascular connection detected in the M. baccata group at day 28. This study confirms that M. hupehensis and M. robusta are superior compatible rootstocks for M. ‘Huabiao’, and the dynamic levels of the three physiological indices can serve as potential indicators for evaluating crabapple graft compatibility.
The containerized production of grapevines has increased recently in the United States. Using container systems is a paramount consideration for nursery profitability and plant growth. Nurseries aim for a system that optimize greenhouse space and shipping costs, while maintaining transplant quality. Limited research has been conducted on the effects of container systems on grapevine growth and physiology traits. The goal of this study was to evaluate the effects of commercially used container systems in US nurseries on plant biomass, root morphology, and leaf function during nursery production. One-year old own-rooted ‘Concord’ and ‘Traminette’ grapevines were grown for 104 days in three commercial nursery container systems: ‘small’ (7.6 × 20 cm, 1.2 L tapered, internal vertical walls), ‘medium’ (10 × 23 cm, 1.5 L, tapered, internal vertical walls), and ‘large’ (15 × 40 cm, 4.4 L, rectangular, smooth-walled). Neither shoot nor root dry weights were affected by the container system in any of the cultivars; similarly, the root morphology of none of the cultivars was affected by the container system. The container system did not impact leaf function (photosynthetic rate, transpiration rate, stomatal conductance) observed; however, small container systems led to lower chlorophyll content in both cultivars. Our study suggests that all tested container systems are applicable for grapevine nurseries.
Climate change strongly impacts the physiological processes in the grapevine. Two Romanian autochthonous cultivars, Șarba and Fetească neagră (Vitis vinifera L.), grown under semi-arid conditions in 2024 (De Martonne Index: 23.6; Hydrothermal Coefficient: 0.75), showed different physiological behaviours. Leaf gas exchange parameters (A, gs, E, Ci) and water use efficiency (WUE) were assessed at three phenophases (flowering, berry growth, and véraison), while photosynthetic pigment indices (Chl a/b, Chl/C+X) and leaf dry matter content (dm) were additionally determined at harvest maturity. Multivariate analysis consistently separated the two cultivars into distinct physiological groups: responses consistent with near-isohydric behaviour in Șarba and anisohydric behaviour in Fetească neagră, based on gas-exchange parameters interpreted within the established isohydric/anisohydric framework, as direct water potential measurements were not performed. Șarba exhibited a water-conserving strategy at véraison—characterised by early stomatal closure, high WUE, and maintained chlorophyll—protecting vine water status at the cost of reduced leaf carbon assimilation. Fetească neagră, by contrast, kept its stomata progressively open, sustaining high gas exchange rates in a pattern consistent with progressively declining shoot water potential. Berry sugars are expected to concentrate passively late in ripening, while severe deficit risks berry shrivelling and, under prolonged drought, premature senescence of basal leaves, to our knowledge, a phenomenon not previously reported for this cultivar. These findings support cultivar-specific management, with implications for irrigation scheduling and varietal selection under climate change.
Sugar beet (Beta vulgaris L.) is a major sugar-producing crop worldwide, yet rhizomania, root-knot nematode, and root rot diseases severely constrain its yield and quality. Screening resistant germplasm is critical for disease-resistant breeding and sustainable sugar beet production. In this study, we evaluated the disease resistance of 96 introduced sugar beet cultivars via molecular marker assays and field disease nursery trials. The results showed that 76 cultivars (79.2%) carried the strong resistance genotype for rhizomania, and 20 cultivars (20.8%) carried the weak resistance genotype. For root-knot nematode, 87 cultivars (90.6%) were heterozygous resistant, while 9 cultivars (9.4%) were homozygous susceptible; no homozygous resistant genotype was detected in this study. Field evaluation of root rot showed that disease incidence ranged from 15.45% to 100%. Only one cultivar (KWS7772) was rated as resistant (R), accounting for 1.0%, and two cultivars were moderately resistant (MR), accounting for 2.1%. Among all tested cultivars, KWS7748 showed combined resistance to rhizomania, root-knot nematode, and root rot. These findings provide candidate resistant germplasm resources and baseline resistance data under the tested conditions for sugar beet disease resistance breeding; further multi-environment and multi-year validation is needed, particularly for root rot resistance, before these varieties can be recommended for commercial deployment.
Cassava is a crop of major socioeconomic and cultural importance in Colombia. One of the main challenges is production seasonality, driven by climatic conditions that constrain planting and harvesting periods. Currently, cultivated varieties exhibit a substantial reduction in root dry matter content (DMC) following the onset of the rains. This study evaluated the agronomic performance of genotype SM2828-28 under semi-commercial field conditions in the departments of Cesar, Bolívar, and Magdalena in the Colombian Caribbean region. This genotype exhibited greater stability and productivity, outperforming commercial checks. The genotype also showed high and stable DMC. Root quality and starch functional properties were also assessed. Starch from SM2828-28 exhibited numerically lower setback values and a relatively consistent rheological profile across harvest ages, indicating greater gel stability during cooling—an attribute desirable for industrial applications requiring consistent textural properties. The genetic progress achieved for key industrial traits highlights the potential of SM2828-28 for extended-harvest systems aimed at reducing seasonality in raw material supply for the cassava starch industry. These results suggest that genetic factors contribute to the stability of DMC under extended-harvest conditions and support the inclusion of this trait as a target in cassava breeding programs.
Bioactive polysaccharide-based edible coatings are promising strategies for maintaining postharvest fruit quality. This study aimed to extract and characterize crude polysaccharides from Brazilian Hovenia dulcis (HDPs-BR) and evaluate their potential as edible coatings, alone or combined with sodium alginate (SA) and eugenol (Eug), for strawberry preservation. HDPs-BR showed an extraction yield of 5.31 ± 0.19%, with 62.68 ± 1.90% total sugars, 24.95 ± 0.39% uronic acids, and 5.33 ± 0.23% proteins. They also contained phenolic compounds and exhibited antioxidant activity. Coating performance depended on formulation and storage period. After 15 days, HDPs-BR 0.5% provided the highest firmness, whereas HDPs-BR 1% favored phenolic and anthocyanin retention and red color. SA-containing formulations showed attribute-dependent benefits: HDPs-BR 0.5% + SA 0.5% promoted high phenolic content, while its combination with Eug 0.1% improved luminosity and antioxidant activity at specific storage periods. HDPs-BR 1% + Eug 0.1% maintained a red color and showed high anthocyanin content and antioxidant activity. Overall, HDPs-BR demonstrated potential as a bioactive edible coating matrix, with formulations containing SA and Eug providing additional benefits depending on the quality attribute evaluated.
Waterlogging stress is a major abiotic stressor that severely constrains crop growth and productivity. Aerenchyma provides intercellular air spaces to transport oxygen to the root, which is essential for survival under waterlogged conditions. However, the mechanism underlying the response to waterlogging and aerenchyma formation in luffa remains poorly understood. In this study, we identified distinct phenotypic responses between two cultivars: ‘Zhonglü’ exhibited aerenchyma formation in the hypocotyl under waterlogging, whereas ‘Yalü’ did not. Transcriptome profiling of ‘Zhonglü’ revealed differentially expressed genes linked to plant hormone signal transduction, including fifteen auxin-related and two jasmonate-related genes, which may be involved in waterlogging-induced aerenchyma formation and are proposed as candidate regulators. Furthermore, exogenous application of 5 μmol/L N-1-naphthylphthalamic acid (NPA) and 20 μmol/L methyl jasmonate (MeJA) significantly enhanced aerenchyma formation. Notably, these treatments uncovered a regulatory node wherein NPA-disrupted auxin transport and jasmonate signaling converge to coordinately fine-tune the expression of ARF18, IAA32, GH3.17 and TIFY9 genes in the hypocotyl. Taken together, this study definitely advances our knowledge of the morphological and transcriptomic responses of Luffa under waterlogging stress and sheds new lights on its adaptive mechanisms.
The HB (homeobox) transcription factor family plays important roles in plant growth, development, morphogenesis, and stress responses; however, its involvement in longan (Dimocarpus longan Lour.) fruit energy metabolism remains unclear. In this study, 32 DlHB family members were identified in the longan genome, and their physicochemical properties, phylogenetic relationships, gene structures, conserved motifs, conserved domains, tissue-specific expression patterns, promoter cis-acting elements, and collinearity relationships were systematically analyzed. The DlHB family was classified into four subfamilies, HD-ZIP I–IV, with substantial divergence in structural composition, expression patterns, and putative regulatory features. Our previous work showed that 1.5% chitosan (CTS) treatment improved postharvest longan fruit quality through modulation of energy metabolism, and the corresponding CTS-treatment transcriptome was therefore used here to screen energy-metabolism-associated DlHB candidates. DlHB22 was selected as a representative candidate, and its CTS-responsive expression was independently confirmed by qRT-PCR. Exogenous ATP treatment was then used as an independent physiological validation of the relationship between energy metabolism and postharvest storability; ATP-treated fruit showed reduced deterioration together with higher ATP, ADP, and AMP contents and higher activities of H+-ATPase, Ca2+-ATPase, cytochrome c oxidase (CCO), and succinate dehydrogenase (SDH) at 15 d, although adenylate energy charge (AEC) was lower than in the control. DlHB22 localized predominantly to the nucleus. Heterologous overexpression of DlHB22 in tomato accelerated fruit color transition and ripening progression and altered ATP, ADP, and AMP contents, AEC, and the activities of H+-ATPase, Ca2+-ATPase, CCO, and SDH. Transcriptome analysis of DlHB22-overexpressing tomato fruit revealed broad transcriptional changes in pathways associated with central carbon metabolism, energy metabolism, glutathione metabolism, hormone signaling, and MAPK signaling, and qRT-PCR validation of six representative DEGs was consistent with the RNA-seq trends. Because tomato is climacteric whereas longan is non-climacteric, the heterologous tomato results demonstrate the regulatory potential of DlHB22 but do not establish an identical native ripening pathway in longan. Overall, DlHB22 is best regarded as a candidate transcription factor associated with longan fruit energy metabolism, whose native regulatory mechanism requires direct validation in longan.
