Fruit acidity, a key quality trait, is primarily determined by malic acid in many fruit crops. However, the molecular machinery governing its accumulation, particularly in response to hormonal cues like auxin, remains a "black box." Here, we systematically deconstruct the regulatory pathway controlling malic acid in litchi (Litchi chinensis). We first identify the tonoplast-localized transporter LcALMT1 as the principal channel for malate sequestration into the vacuole. We then uncover its upstream regulatory module, revealing that the R2R3-MYB transcription factor LcMYB70 directly binds the LcALMT1 promoter but lacks intrinsic transcriptional activity. Instead, LcMYB70 functions as a molecular scaffold to recruit the Auxin Response Factor LcARF10, which confers transcriptional repression upon the complex. This LcMYB70-LcARF10 repressor module is negatively regulated by auxin signaling, providing a direct molecular link between the decline in endogenous auxin during fruit maturation and the attenuation of malate accumulation. Critically, we identified a single-nucleotide polymorphism in the LcARF10 gene that governs the divergence between high- and low-acid cultivars. The functional C allele in low-acid cultivars enables the formation of the repressor complex. In contrast, the T allele in high-acid cultivars contains a premature stop codon that results in a non-functional, truncated protein, preventing complex assembly and causing the high-acid phenotype. Our study defines a complete pathway from hormone to trait and its genetic basis, revealing a novel MYB-ARF scaffold module; a definitive molecular link between auxin withdrawal and metabolic reprogramming; and the functional integrity of a corepressor as a new paradigm for trait diversification.

Low-temperature stress (LTS) inhibits the growth and yield of pitaya. HuBBX1, a cold-tolerance transcription factor, was identified based on the physiological and transcriptomic analyses between two pitaya cultivars. HuBBX1 enhances plant cold tolerance via the activation of cold-regulated (COR) genes. Low-temperature stress (LTS) affects fruit quality and yields. Pitaya plants are sensitive to LTS; however, the molecular mechanisms underlying LTS in pitaya remain poorly understood. In this study, the chlorophyll fluorescence, photosynthetic system, cold tolerance-associated physiological indexes, and differentially expressed genes (DEGs) were compared using two pitaya cultivars, i.e., ‘SCAU-NH’ (resistant to low temperature) and ‘SCAU-KX’ (sensitive to low temperature) at the LTS. Six candidate transcription factors (TFs) related to LTS were identified according to their expression profiles. Yeast growth assay and GUS activity analysis showed that HubZIP6, HuOFP12, HuBBX1, HuHY5, HuBOA1, and HuERF39 could enhance cold resistance. Among them, HuBBX1 is a nuclear protein with transcriptional activation capability. Overexpression of HuBBX1 enhanced cold tolerance in Arabidopsis thaliana and tomato. Dual-luciferase reporter assays (DLR), yeast one hybrid (Y1H), and EMSA showed that HuBBX1 promotes the expression of cold-regulated (COR) genes (HuCOR15A and HuRD29A) by directly bounding to the G-box in their promoters to increase plant cold tolerance. The present work provides a foundation for further study of the molecular mechanisms of pitaya’s response to LTS.

Cold stress severely limits the yield and quality of fruit crops, yet its regulatory mechanisms in pitaya remain poorly understood. Here, we identified a cold-inducible bZIP transcription factor, HubZIP6, that plays a central role in enhancing cold tolerance in pitaya. HubZIP6 is a nuclear-localized protein with transcriptional activation activity, and its overexpression in Arabidopsis and tomato significantly improved cold tolerance, as reflected by higher survival rates, reduced ion leakage, and lower reactive oxygen species accumulation. Mechanistically, HubZIP6 directly binds to ACGT motifs in the promoters of HuCBF1 and HuCBF3, thereby activating their expression under cold stress. In addition, HubZIP6 physically interacts with the salicylic acid-binding protein HuSABP2, which synergistically enhances the transcriptional activation of HuCBF genes. Notably, HubZIP6 also directly activates HuSABP2, forming a regulatory loop that connects CBF transcriptional control with salicylic acid signaling. Consistently, overexpression of HuSABP2 further enhances cold tolerance in transgenic plants. Collectively, these findings demonstrate that cold tolerance is enhanced through HubZIP6-mediated integration of CBF activation and salicylic acid signaling, providing a promising genetic target for improving stress resilience in fruit crops.

Seed abortion is a critical agronomic trait affecting both fruit quality and yield. Cell wall invertase (CWIN) hydrolyzes sucrose into glucose and fructose, which serve as both nutrients and signaling molecules to regulate seed development, with its activity suppressed by invertase inhibitor (INH). However, the transcriptional regulators controlling INH expression remain unknown. Here, we identify the MADS-box transcription factor LcMADS28 as a direct activator of LcINH1. LcMADS28 is highly expressed in the funicle and embryo of the abortive-seeded cultivar 'Nuomici' at 15 days after anthesis, whereas its expression is much lower in the big-seeded cultivar 'Heiye'. Further analysis reveals that LcMADS28 interacts with LcMADS27 to form a heterodimer that directly binds to the LcINH1 promoter and activates its transcription. Silencing LcMADS28 in 'Nuomici' reduces LcINH1 expression, which increases CWIN activity, promotes embryo and seed development, and lowers fruit abscission. RNA-seq analysis indicates that genes associated with auxin and sucrose metabolism are activated after LcMADS28 silencing. In addition, heterologous overexpression of LcMADS28 in tomato and Arabidopsis increases seed abortion. Together, our results indicate that LcMADS28 and LcMADS27 coordinately activate LcINH1 to regulate early seed development in lychee and provide a mechanistic framework linking MADS-box transcription factors with the invertase/INH module.

Fruit quality in wampee is strongly influenced by the accumulation of key metabolites, including anthocyanins, sugars, and organic acids, yet their metabolic dynamics during fruit development remain poorly understood. In this study, we analyzed metabolite profiles and the expression of metabolism-related genes in the pulps of two wampee cultivars, “Jixin” (JX) and “Zirou” (ZR), across multiple fruit developmental stages. Two anthocyanins, 17 sugars, and 32 organic acids were identified. Total phenolics, flavonoids, starch, and soluble sugars accumulated mainly during early fruit development. “JX” wampee exhibited higher ascorbic acid levels than “ZR” wampee. Sucrose and citric acid were the predominant sugars and organic acids in both cultivars. Transcriptomic analysis revealed 37 anthocyanin-related, 29 sugar-related, and 18 organic acid-related genes. Strong correlations between candidate gene expression and metabolite levels suggest that these genes play key roles in regulating the biosynthesis and accumulation of anthocyanins, sugars, and organic acids in wampee.

Litchi chinensis Sonn. is an important economic fruit tree in tropical and subtropical regions. Regrettably, the efficiency of plant regeneration via somatic embryogenesis in litchi is typically low due to the poor conversion of embryos to plants. The purpose of this study was to establish a regeneration system via somatic embryogenesis from immature embryos explants in 'Heiye' cultivar of litchi. Our results demonstrated that MS medium supplemented with 2.0 mg L-1 2,4-D was optimal for callus induction. For somatic embryo (SE) induction, MS medium containing 0.5 g L-1 activated charcoal (AC) was the most effective, while the use of zeatin (ZT) and thidiazuron (TDZ) resulted in abnormal somatic embryos. The rooting and regeneration rate of 2.15% and 17.5%, respectively, were achieved using MS medium supplemented with 0.5 g L-1 AC. Furthermore, transcriptome analysis was performed on embryogenic callus (EC), globular embryo (GE), and heart embryo (HE) to explore the molecular mechanisms of early somatic embryogenesis. 2,587 common differentially expressed genes (DEGs) between EC_vs_GE and EC_vs_HE were identified, and the expression patterns of these common DEGs were separated into twelve major clusters. GO annotation and KEGG pathway analysis revealed that these common DEGs were implicated in plant hormone signal transduction, auxin-activated signaling pathway, and other biological processes. Additionally, differentially expressed transcription factors were identified, and the function of LcBBM2 which is specifically highly expressed during early somatic embryogenesis was verified. Overexpression of LcBBM2 in tomato promotes callus and shoot formation. Therefore, this study can provide a theoretical basis and technical support for genetic breeding improvement of litchi.

Wampee (Clausena lansium), a tropical evergreen fruit from the Rutaceae family renowned for its rich nutrient profile and bioactive compounds, presents a fascinating case study in fruit coloration. However, changes in anthocyanins, and expressions of metabolism-associated genes during fruit maturation of red-pericarp wampee ('ZR') are not documented. In this study, metabolic and gene expression profiles of anthocyanin across different fruit developmental stages of red and yellow-pericarp wampees were analyzed. A total of 38 distinct anthocyanins were identified from the comparison of 'ZR3' and 'JX3' wampees and categorized into 17 differential anthocyanin metabolites (DAMs). Among these DAMs, fifteen were up-regulated in 'ZR3', while two were down-regulated compared with 'JX3'. The delphinidin 3-[6-(4-(caffeoylrhamnosyl)glucoside)] was the predominant anthocyanins in 'ZR' wampee. A total of 1135 metabolics mainly including amino acid metabolites and flavonoids were detected in the 'ZR' and 'JX' wampees. Significant differences were mainly concentrated in the biosynthesis of secondary metabolites in terms of flavonoid biosynthesis, ABC transporters, and anthocyanin biosynthesis. According to the combined analyses of qRT-PCR and transcriptome, the transcript levels of PAL1, PAL2, CHS1 and UFGT1 in 'ZR' wampee were two to eight-fold higher than those in 'JX' wampee during fruit pigmentation. Our study offers valuable insights into the mechanisms of anthocyanin accumulation in the red pericarp of wampee which is helpful to regulate fruit coloration of wampee.

Basic helix-loop-helix (bHLH) proteins have been recognized as activators of anthocyanin in many plant species, but their role as inhibitors of anthocyanin is seldom reported. In this study, LcbHLH107 was identified as a transcription repressor regulating anthocyanin biosynthesis in litchi. LcbHLH107 was up-regulated in the red hairy roots overexpressing LcMYB1, which was the key transcription activator in litchi anthocyanin biosynthesis. Dual luciferase assay and yeast one-hybrid assay confirmed that LcbHLH107 was regulated by LcMYB1. LcbHLH107 could suppresses anthocyanin accumulation through transient transformation in petunia leaves and overexpression in litchi callus. Moreover, LcbHLH107 directly bound to the promoter of LcDFR, and inhibited its expression. Furthermore, protein sequence mutation and functional verification revealed that the EAR motif was essential for the inhibitory function of LcbHLH107. In summary, LcbHLH107 is a repressor that inhibits anthocyanin biosynthesis in litchi, providing a negative feedback mechanism to regulate anthocyanin accumulation at transcriptional level.

Pitaya is an important perennial herbaceous fruit tree. The color of fruit determines pitaya nutritive (and attractive) value, which is considered as an important objective in breeding improvement. In this study, we reported the first telomere-to-telomere (T2T) gap-free genome of "Shuangse No. 1" pitaya (Hylocereus polyrhizus; red peel). Two high-quality genomes for "Dahong" (H. polyrhizus; red peel) and "Honghuaqinglong" (H. stenopterus; stay-green) were further assembled, aiming to explore the genetic diversity of pitaya genomes. In further analysis, we noticed a high proportion of viral contamination in pitaya tissues, which hindered the efficient utilization of transcriptomic data. To address this issue, we analyzed 111 pitaya transcriptome data from different geographic regions to characterize and separate viral components. Then we developed an efficient, novel, and universal transcript purification system for pitaya transcriptomes by applying it to 27 samples from different tissues and species, thereby enhancing the utility for transcriptomic and broader biological research. Combining the purified transcriptomic data with comparative genomic analyses, we identified HuERF72, a transcription factor (TF) that potentially regulates chlorophyll degradation in pitaya. Interaction assays and plant transformation elucidated that HuERF72 acts as a repressive TF by directly binding to the promoter of HuSGR1, a key structural gene in the chlorophyll degradation pathway. This study provides high-quality genomic resources and novel methodologies for molecular investigations in pitaya. Additionally, the proposed regulatory network advances our understanding of the transcriptional regulatory mechanisms underlying chlorophyll degradation, offering valuable insights into the genetic improvement of pitaya.

Glycosylation of anthocyanin plays an important role in increasing its stability and diversity in plants. Here, we identified a glucosyltransferase gene responsible for the anthocyanin components in Litchi chinensis Sonn. Cyanidin-3-rutinoside is the main anthocyanins of pericarps and red hairy roots overexpressing MYB transcription factor LcMYB1 in the late maturing cultivars. However, in the early maturing cultivars, the anthocyanins in the pericarps is dominated by cyanidin-3-glucoside, and the anthocyanins in the red hairy roots overexpressing LcMYB1 is dominated by cyanidin-3-rutinoside. Enzyme assays highlighted notable differences in flavonoid 3-O-rhamnosyltransferase (F3RT) activity between the pericarps and red hairy roots overexpressing LcMYB1 in the early maturing cultivars. Two differentially expressed genes (DEGs), LcF3RT1 and LcF3RT2, were significantly up-regulated in the red hairy roots overexpressing LcMYB1. Yeast one-hybrid and dual luciferase reporter assays revealed that LcMYB1 could bind to the promoter of LcF3RT2 and significantly activate its expression. Functional validation showed that LcF3RT2 could catalyze the conversion of cyanidin-3-glucoside into cyanidin-3-rutinoside, leading to the differences on anthocyanin components in pericarps and red hairy roots of early maturing litchi cultivars. Our results will provide insights into the regulation and glycosylation modification of anthocyanins in litchi as well as in other plants.

Polyploidy in plants can enhance stress resistance and secondary metabolite production, offering potential benefits for Clausena lansium (L.) Skeel, a medicinally valuable species. However, systematic studies of polyploidy-induced morphological, anatomical, and metabolic changes in this species are lacking. This study aimed to induce and characterize polyploid C. lansium lines, assess ploidy-dependent variations, and evaluate their impact on bioactive metabolite accumulation. Three cultivars were hybridized, treated with colchicine, and bred, yielding 13 stable polyploid lines confirmed by flow cytometry and chromosome counting. The polyploids exhibited distinct traits, including larger pollen grains, altered leaf margins, increased leaflet numbers, enlarged guard cells with reduced stomatal density, and thicker leaf tissues. Metabolomic analysis revealed that tetraploids accumulated significantly higher levels of flavonoids, alkaloids, and phenolic acids compared to diploids, while triploids showed moderate increases. These findings demonstrate that polyploidization, particularly tetraploidy, enhances C. lansium’s medicinal potential by boosting pharmacologically active compounds. The study expands germplasm resources and supports the development of high-quality cultivars for pharmaceutical applications.

Fruit size is an important quantitative trait that directly affects yield and quality. However, fruits are generally small in the current main litchi cultivars, which seriously influence yield. In this study, we characterized the fruit phenotype and histology of large-fruited cultivars 'Ziniangxi' (ZNX) and 'Hehuadahongli' (HHDHL) and smallfruited cultivars 'Chenzi' (CZ) and 'Guiwei' (GW) at different developmental stages. Large-fruited cultivars (ZNX and HHDHL) had greater pericarp weight and thickness, aril weight, aril cell size, seed weight, and seed cell size compared to small-fruited cultivars (CZ and GW). ZNX had the largest single fruit weight at maturity, while CZ had the smallest fruit size. Then, the pericarps, arils, seeds, and the early developing fruits of CZ and ZNX at different developmental stages were used for transcriptome sequencing to unravel the mechanism underlying fruit size in litchi. A total of 21,672 DEGs were identified by pairwise comparisons of young fruits, pericarp, aril, and seeds at each developmental stage between CZ and ZNX cultivars. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that numerous genes associated with cytokinin, auxin, gibberellin and brassinosteroid exhibited differential expression between large- and smallfruited litchi cultivars, such as LcBEH2, LcIPT, LcGH3.1, LcCYP72A219. These results provide a theoretical basis for the regulation of fruit size in litchi breeding.

Salicylic acid (SA) serves as an intercellular signaling molecule, playing a crucial role in plant growth and development, along with the response to environmental stressors. However, molecular regulations that govern salicylic acid-induced resistance to drought in plants remain incompletely elucidated. This research utilized two-year-old C. camphora seedlings as the experimental subjects, employing a two-factor experimental design that incorporated soil moisture×salicylic acid spraying. Through a combination of physiological and transcriptomic analyses, it aimed to elucidate the mechanisms by which exogenous salicylic acid influences the growth and physiological traits of C. camphora seedlings subjected to drought stress, as well as the regulation of salicylic acid-mediated drought-related signaling pathways. Research indicates that SA can markedly improve the substance called chlorophyll fluorescence parameters (that is, Fv/Fm and PIabs) of C. camphora subjected to drought stress, augment photosystem activity during mild drought conditions, and mitigate the damage inflicted by excessive light energy in photosynthetic institutions. SA significantly alleviated oxidative stress in C. camphora seedlings under drought stress by reducing O2- and H2O2 contents and enhancing SOD, POD, and CAT activities. Transcriptome analysis revealed that SA induces DEGs associated with drought resistance. It activates transcription factors that are attached as NAC, bHLH, ERF, and MYB, and regulates genes involved in plant hormone signaling, such as AUX/IAA, PYR/PYL, A-ARRs, and B-ARRs. Additionally, it suppresses the degradation of starch, enhances the expression of genes associated with photosynthesis, and alleviates the adverse effects during conditions of drought that negatively impact the photosynthetic performance of C. camphora, thus enhancing their resilience to drought conditions. Furthermore, SA significantly affected phenylpropanoid synthesis-related genes (such as CcHCT, CcPOD, and CcCOMT). This research seeks to improve understanding of the mechanisms by which SA influences drought tolerance in plants, providing novel insights into enhancing drought resistance in C. camphora.

Soluble sugar is an important factor in determining fruit quality and flavor. In this study, the sugar accumulation mechanisms in wampee (Clausena lansium) fruits were investigated by using two cultivars-'Huami' (sweet) and 'Jinjixin' (sweet and sour)-at five developmental stages. Transcriptome analysis revealed a strong correlation between ClSWEET3a expression and total soluble sugar/sucrose content. Functional characterization demonstrated that ClSWEET3a, a plasma membrane-localized transporter, facilitates glucose and sucrose uptake in yeast. Silencing of ClSWEET3a in 'Jinjixin' fruits significantly decreased both sucrose and hexose levels, confirming its role in sugar accumulation. Furthermore, we identified two transcription factors (ClbZIP3 and ClERF062) that activate the ClSWEET3a promoter, with ClbZIP3 exhibiting stronger regulatory effects. Yeast one-hybrid assays confirmed their direct binding to the ClSWEET3a promoter. Our findings elucidate a molecular framework for sugar accumulation in wampee and provide insights for targeted breeding strategies to improve fruit quality.

Genetic breeding and molecular identification in varieties depend on high-performance genotyping tools. The high heterozygosity of the litchi genome contributes to increased resequencing costs and elevated error rates in hybridization-based genotyping methods. In this study, a liquid chip named Litchi40K v1.0 was developed with high-depth resequencing data from 875 litchi samples, and its efficacy was validated across three different populations. In the L. chinensis var. fulvosus population, three subpopulations characterized by spatial distribution, and a total of 1110 genes were identified in the genomic regions with subpopulation differentiation. Additionally, a total of 30 significant signals associated with diverse agronomic traits were identified. The H002 haplotype of LITCHI02696, dominant in the Sub2 subgroup, significantly increased the soluble solid content in the L. chinensis var. fulvosus population. In a hybrid F1 population, a high-density genetic map was constructed and 79 dwarfing-related QTLs were identified with the liquid chip. An NAC transcription factor was identified as a candidate gene with a heterozygous frameshift variant in the male parent. To facilitate the digitization of germplasm resources, 384 SNPs were selected, and the DNA fingerprint map revealed clear genetic relationships and a total of 10 potential synonym groups or instances of bud mutations were identified in 164 main cultivated litchi varieties. This study provides cost-effective, flexible, and versatile liquid chip for genetic analysis and digitalization of germplasm resources in litchi.

Litchi has great economic significance as a global fruit crop. However, the advancement of litchi functional genomics has encountered substantial obstacles due to its recalcitrance to stable transformation. Here, we present an efficacious Agrobacterium tumefaciens-mediated transformation system in somatic embryos of ‘Heiye’ litchi. This system was developed through the optimization of key variables encompassing explant selection, A. tumefaciens strain delineation, bacterium concentration, infection duration, and infection methodology. The subsequent validation of the transformation technique in litchi was realized through the ectopic expression of LcMYB1, resulting in the generation of transgenic calli. However, the differentiation of transgenic calli into somatic embryos encountered substantial challenges. To delineate the intricate molecular underpinnings of LcMYB1’s inhibitory role in somatic embryo induction, a comprehensive transcriptome analysis was conducted that encompassed embryogenic calli (C), globular embryos (G), and transgenic calli (TC). A total of 1,166 common differentially expressed genes (DEGs) were identified between C-vs.-G and C-vs.-TC. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that these common DEGs were mostly related to plant hormone signal transduction pathways. Furthermore, RT-qPCR corroborated the pronounced down-regulation of numerous genes that are associated with somatic embryo induction within the transgenic calli. The development of this transformation system provides valuable support for functional genomics research in litchi.

ABSTRACT Oomycete pathogens secrete hundreds of RXLR effectors into plant cells to modulate host immunity by targeting diverse plant proteins. Here, we report that the Peronophythora litchii RXLR effector PlAvh133 acts as a virulence factor and targets the litchi glycolate oxidase (GLO) LcGLO1, a key enzyme in photorespiration, thereby suppressing plant immunity. PlAvh133 localises to the plasma membrane (PM) in planta, and its first α‐helix is vital for both its LcGLO1‐binding activity and proper PM localisation. LcGLO1 is mainly confined to the peroxisomes, and its overexpression significantly enhanced resistance to downy blight in litchi. Conversely, silencing the Nicotiana benthamiana homologue of LcGLO1 increases plant susceptibility to the oomycete pathogen. Critically, PlAvh133 causes the relocation of LcGLO1 from peroxisomes to the PM and inhibits its enzymatic activity, leading to increased plant susceptibility. PM‐localised LcGLO1 cooperates with catalase (CAT) LcCATB to suppress reactive oxygen species (ROS) burst. Meanwhile, PM‐localised LcGLO1 destabilises respiratory burst oxidase homologue (RBOH) LcRBOHD by interacting with calcium‐dependent protein kinase (CPK) LcCPK5, further reducing ROS production. Taken together, our findings unveil an unprecedented virulence mechanism by which a pathogen effector relocalises and inhibits host GLO1 activity, thereby simultaneously diminishing ROS production from both the peroxisomes and PM‐localised RBOHD.

BACKGROUND:Fruit acidity, a crucial determinant of flavor and quality, is primarily governed by the content and composition of organic acids, with citric acid playing a dominant role. To unravel the molecular basis of citric acid accumulation, we analyzed four wampee (Clausena lansium) cultivars-sweet-type 'Huami' and 'Baitang' and sweet-sour-type 'Huami 2' and 'Wuhe'-by integrating transcriptomic data with organic acid profiling. Candidate genes were systematically screened based on their expression patterns and correlations with acid content. RESULTS:Transcriptome analysis identified three key regulators of citric acid accumulation: ClVHP1 (encoding a vacuolar H+-phosphatase), ClMYB5, and ClbHLH42, all exhibiting strong expression-acidity correlations. Subcellular localization confirmed the nuclear presence of ClMYB5 and ClbHLH42, while transient overexpression in tomato validated their functional roles, consistently elevating citric acid levels. Conversely, virus-induced gene silencing (VIGS) of these factors markedly reduced acid accumulation. Mechanistically, we demonstrated that ClMYB5 directly binds the ClVHP1 promoter to activate its expression, thereby enhancing vacuolar acid sequestration via ClVHP1's proton-pump activity. However, the ClbHLH42 participates in the acid regulation but indirect. CONCLUSIONS:Our study establishes a coordinated regulatory module wherein ClMYB5, ClbHLH42, and ClVHP1 collectively govern citric acid storage in wampee. The discovery of ClMYB5-mediated ClVHP1 activation provides novel insights into vacuolar acid partitioning. These findings not only advance the understanding of organic acid metabolism but also offer strategic targets for precision breeding of fruit quality traits.

NAC (NAM, ATAF1/2 and CUC) transcription factors represent one of the largest plant specific transcription factor families, playing crucial roles in plant growth and development. Chlorophyll, a vital pigment in plant photosynthesis, diminishes during fruit ripening and plant senescence. In this study, we identified 114 NAC genes from the litchi genome. LcNACs were found to be clustered, paired, and independently distributed on chromosomes, and classified into 7 groups. Collinearity analysis revealed that 15 gene pairs, involving 26 LcNACs, resulted from segmental duplication events. Based on transcriptome data, clustering and correlation analysis, LcNAC025, LcNAC038, and LcNAC087 were identified as key players in chlorophyll degradation. As transcriptional activators located in the nucleus, they were shown to directly bind to the promoters of LcNYC, LcPAO, and LcSGR, activating their expression. Moreover, transient overexpression of LcNAC025, LcNAC038, and LcNAC087 in tobacco leaves promoted chlorophyll degradation and up-regulated the expression of NbNYC, NbPPH, NbPAO, and NbSGR. In summary, this study highlights the molecular roles of LcNAC025, LcNAC038, and LcNAC087 in regulating chlorophyll degradation during litchi fruit ripening.

Pitaya is a tropical and subtropical fruit; it can produce several batches fruit in one year. To find out the fruit quality differences between various batches in the same year in Guangzhou, South China, 11 pitaya varieties were used as the materials. Comparative analysis was performed between these varieties of each batch by 14 indexes, comprehensive evaluation and ranking were evaluated by the principal component analysis (PCA). Results showed that the red-peel and red-pulp pitaya has the longer fruit period and could obtain more batches fruits. By comparing the fruit quality of these 11 varieties in different batches: Except "Guanhuahong," fruit weight is significant different between other 10 varieties. The edible rate of fruits from 2(nd) and 3(rd) batches is significantly higher than others. The hardness, total sugar, total acid, betalain, total phenol, and flavonoids were significant difference between batches. The PCA results indicated that in most varieties, the 1(st), 8(th), 9(th) batches are generally with heavier fruit, better color, harder and sweeter; more stable antioxidant compounds were shown in 6(th), 7(th), 8(th), 9(th) batches; the 3(rd), 4(th), 5(th), and 6(th) batches are smaller, softer, lower soluble sugar and higher titratable acid. Pitaya fruit quality and tastes from various batches are different in the same year, the climate may be the main factor. The fruits of 7(th), 8(th) and 9(th) batches picking from Sep to Nov has better quality and higher economic value. This research has practical application value and could provide theoretical basis for the production of pitaya.