Shoot branching, a major determinant of plant architecture and productivity, has long been attributed to the coordinated action of auxin, cytokinins (CKs), and strigolactones (SLs). Recent work shows that sugars act not only as metabolic resources but also as early developmental signals that regulate axillary bud outgrowth, the initial step in shoot branching. Sugar availability can rapidly trigger bud outgrowth, often preceding major hormonal changes. Mechanistically, sugars antagonize auxin and SL signaling while acting synergistically with CKs. These effects involve sugar signaling pathways mediated by trehalose 6-phosphate (Tre6P) and HEXOKINASE1 (HXK1), as well as metabolic reprogramming of glycolysis, the tricarboxylic acid (TCA) cycle, and the oxidative pentose phosphate pathway (OPPP). The transcription factor BRANCHED1/TEOSINTE BRANCHED1 (BRC1/TB1) participates in this regulatory network by integrating specific sugar and hormonal inputs involved in the control of the transition between bud dormancy and bud outgrowth. Here, we synthesize current knowledge on the interplay between sugar metabolism, sugar signaling, and hormonal pathways in regulating bud fate and highlight key questions that will shape future research in this field.

In strawberry, the axillary bud (AXB) can produce either an elongated stem called stolon giving a daughter-plant (asexual reproduction) or an inflorescence-bearing branch crown (BC) (sexual reproduction). The fate of the AXB depends on node position on the axis and on genetic and environmental factors. Here, in Fragaria vesca, we addressed the largely unanswered question of how molecular factors determine AXB fate. To get insights into the mechanisms already at play in a morphologically indistinguishable (undifferentiated) AXB, depending on its fate, we combined (1) the phenotypic characterization of AXB development throughout plant growth with (2) the RNA-seq analysis of undifferentiated AXBs, using three different genotypes producing either BCs or stolons (fvetfl1 and fvega20ox mutants, FveFT3 overexpressor). Results allowed the identification of genes regulating AXB fate and outgrowth, among which FveBRC1. The analysis of FveBRC1 expression in genotypes combining various traits (perpetual/seasonal flowering; runnering/runneless) and the generation of CRISPR/Cas9 brc1 mutants further demonstrated that FveBRC1 plays a central role in the determination of AXB fate in strawberry, in addition to its well-known function in BC outgrowth. These original results provide new insights into the determination of AXB fate and, consequently, the control of fruit yield in strawberry. ### Competing Interest Statement The authors have declared no competing interest.

Plants continuously integrate metabolic and hormonal signals to coordinate growth, development, and responses to environmental stimuli. Among these signals, sugars and strigolactones (SLs) have emerged as central regulators. Beyond serving as metabolic fuels, sugars act as signaling molecules that govern key developmental transitions and stress responses. SLs, a relatively recent addition to the phytohormone family, play pivotal roles in shaping plant architecture, modulating resource allocation, and facilitating environmental adaptation. While the individual signaling functions of sugars and SLs are well documented, their crosstalk remains an emerging and largely underexplored area of plant biology. This review synthesizes current knowledge on both the independent and interactive roles of sugar and SL signaling across critical developmental processes, including seed germination, hypocotyl elongation, root and shoot architecture, flowering, senescence, and plant responses to abiotic and biotic stress. By analyzing antagonistic and synergistic interactions, we point out several potential integrative hubs where metabolic and hormonal signals converge to fine-tune the final decision. Notably, the nodal roles of BRC1/TB1 (BRANCHED1/TEOSINTE BRANCHED1), FT (FLOWERING LOCUS T), in mediating sugar-SL crosstalk in shoot branching, flowering, respectively, are highlighted. We also explore how sugar-SL interplay influences seed germination and plant adaptation to environmental stresses through shared regulators such as TOR (Target of Rapamycin) kinase, SnRK1 (Sucrose non-fermenting-1 Related Kinase 1), and SMXLs (Suppressor of MAX2-Like proteins). Understanding these interactions not only deepens our knowledge of fundamental plant biology but also offers new insights for improving the performance and resilience of crop and horticultural species.

Shoot branching is a key process of plant growth and development, finely controlled by cytokinin and sugars. However, cytokinin fails to induce bud outgrowth in the absence of sugar, and so far nothing is known about its ability to antagonize auxin when sugar availability is limited. Here we demonstrate in rose that cytokinin requires sugar metabolism and signalling to promote bud outgrowth, to down-regulate the expression of RhBRC1, a transcription factor gene that inhibits axillary bud growth, and to antagonize the inhibitory effect of auxin on bud outgrowth. Cytokinin regulation of bud sink strength was tightly associated with sugar metabolism, which was evidenced by the expression of genes involved in sugar metabolism [e.g. glycolysis, the tricarboxylic acid, and the oxidative pentose phosphate pathway (OPPP)], a metabolomic approach, and the quantification of total carbon and nitrogen in buds. Cytokinin supply is associated with a significant up-regulation of the OPPP and nitrogen accumulation. Meanwhile, sugar up-regulated bud sensitivity to cytokinin, associated with a significant down-regulation of the cytokinin signalling regulator RhARR1. These findings highlight the key role of sugar metabolism and signalling in cytokinin-induced bud outgrowth and provide new insights into the importance of nutrient-hormone crosstalk in the regulation of shoot branching.

Soil salinity induces osmotic stress and ion toxicity in plants, detrimentally affecting their growth. Potato (Solanum tuberosum) suffers yield reductions under salt stress. To understand salt-stress resilience mechanisms in potatoes, we studied three cultivars with contrasting salt sensitivity: Innovator, Desirée, and Mozart. Innovator emerged as the most resilient under salt stress, displaying minimal reductions in growth and plant tolerance index with no tuber yield loss, despite notable water loss. Conversely, Desirée experienced a significant tuber yield reduction but maintained better water retention. Mozart showed a low plant tolerance index and high water loss. Interestingly, ions measurement across different tissues revealed that, unlike chloride, sodium does not accumulate in tubers under salt stress in these cultivars, suggesting existence of an active sodium exclusion mechanism. A whole root transcriptomic analysis of these cultivars revealed a conserved salt stress response between potato and Arabidopsis. This response includes activation of various abiotic stress pathways and involves sequential activation of various transcription factor families. Root analyses showed that Innovator has lower suberin and lignin deposition, along with stronger K+ leakage in control conditions, resulting in a higher early stress response and increased ABA accumulation shortly after salt stress induction. This could explain Innovator has a more divergent transcriptomic response to salt stress compared to Desirée and Mozart. Nevertheless, Innovator displayed high suberin and lignin levels and ceased K+ leakage after salt stress, suggesting a high acclimation ability. Altogether, our results indicate that acclimation ability, rather than initial root protection against salt prevails in long-term salt-stress resilience of potato.

Shoot branching is determined by a balance between factors that promote axillary bud dormancy and factors that release buds from the quiescent state. The TCP family of transcription factors is classified into two classes, Class I and Class II, which usually play different roles. While the role of the Class II TCP BRANCHED1 (BRC1) in suppressing axillary bud development in Arabidopsis thaliana has been widely explored, the function of Class I TCPs in this process remains unknown. We analyzed the role of Class I TCP14 and TCP15 in axillary branch development in Arabidopsis through a series of genetic and molecular studies. In contrast to the increased branch number shown by brc1 mutants, tcp14 tcp15 plants exhibit a reduced number of branches compared with wild-type. Our findings provide evidence that TCP14 and TCP15 act by counteracting BRC1 function through two distinct mechanisms. First, they indirectly reduce BRC1 expression levels. Additionally, TCP15 directly interacts with BRC1 decoying it from chromatin and thereby preventing the transcriptional activation of a set of BRC1-dependent genes. We describe a molecular mechanism by which Class I TCPs physically antagonize the action of the Class II TCP BRC1, aligning with their opposite roles in axillary bud development.

### Competing Interest Statement The authors have declared no competing interest.

Greenhouse gas (GHG) emissions have created a global climate crisis which requires immediate interventions to mitigate the negative effects on all aspects of life on this planet. As current agriculture and land use contributes up to 25% of total GHG emissions, plant scientists take center stage in finding possible solutions for a transition to sustainable agriculture and land use. In this article, the PlantACT! (Plants for climate ACTion!) initiative of plant scientists lays out a road map of how and in which areas plant scientists can contribute to finding immediate, mid-term, and long-term solutions, and what changes are necessary to implement these solutions at the personal, institutional, and funding levels.

Glucose-6-phosphate dehydrogenase (G6PDH) catalyzes a metabolic hub between glycolysis and the pentose phosphate pathway (PPP), which is the oxidation of glucose-6-phosphate (G6P) to 6-phosphogluconolactone concomitantly with the production of nicotinamide adenine dinucleotide phosphate (NADPH), a reducing power. It is considered to be the rate-limiting step that governs carbon flow through the oxidative pentose phosphate pathway (OPPP). The OPPP is the main supplier of reductant (NADPH) for several “reducing” biosynthetic reactions. Although it is involved in multiple physiological processes, current knowledge on its exact role and regulation is still piecemeal. The present review provides a concise and comprehensive picture of the diversity of plant G6PDHs and their role in seed germination, nitrogen assimilation, plant branching, and plant response to abiotic stress. This work will help define future research directions to improve our knowledge of G6PDHs in plant physiology and to integrate this hidden player in plant performance.

Recent evidence suggests that numerous similarities exist between the genomic landscapes of both conjunctival and cutaneous melanoma. Since alterations of several components of the MAP kinases, PI3K/mTOR, and cell cycle pathways have been reported in conjunctival melanoma, we decided to assess the sensitivity of conjunctival melanoma to targeted inhibition mostly of kinase inhibitors. A high content drug screening assay based on automated fluorescence microscopy was performed in three conjunctival melanoma cell lines with different genomic backgrounds with 489 kinase inhibitors and 53 other inhibitors. IC50 and apoptosis induction were respectively assessed for 53 and 48 compounds. The genomic background influenced the response to MAK and PI3K/mTOR inhibition, more specifically cell lines with BRAF V600E mutations were more sensitive to BRAF/MEK inhibition, while CRMM2 bearing the NRASQ61L mutation was more sensitive to PI3k/mTOR inhibition. All cell lines demonstrated sensitivity to cell cycle inhibition, being more pronounced in CRMM2, especially with polo-like inhibitors. Our data also revealed new vulnerabilities to Hsp90 and Src inhibition. This study demonstrates that the genomic background partially influences the response to targeted therapy and uncovers a large panel of potential vulnerabilities in conjunctival melanoma that may expand available options for the management of this tumor.

AIMS:Conjunctival and cutaneous melanoma partially share similar clinical and molecular backgrounds. As 5-hydroxymethylcytosine (5-hmC) loss has been demonstrated in cutaneous melanoma, we decided to assess if similar changes were occurring in conjunctival melanoma.METHODS:5-methylcytosine (5-mC), 5-hmC and TET2 were respectively identified by immunohistochemistry and RNA ISH in 40 conjunctival nevi and 37 conjunctival melanomas. Clinicopathological correlations were established.RESULTS:5-mC, TET2 and 5-hmC were respectively identified in 67.5%, 95% and 100% of conjunctival nevi and in 81.1%, 35.1% and 54% of conjunctival melanomas. A significant 5-hmC and TET2 loss was identified in conjunctival melanoma comparing to nevus, as well as a significant correlation between TET2 and 5-hmC expression. In the melanomas, 5-hmC expression was only significantly associated with local lymphatic invasion, but not with other clinicopathological parameters. There was a correlation between TET2 expression and the localization of the tumors. 5-mC expression was not associated with any clinicopathological parameters.CONCLUSIONS:We identified a significant 5-hmC loss in conjunctival melanoma similar to cutaneous melanoma. This loss may possibly be attributed to TET2 loss or IDH1 mutations. 5-hmC loss in conjunctival melanoma may help in the differential diagnosis between atypical conjunctival nevus and conjunctival melanoma.

Mitogen-activated protein kinases (MAPK) play pivotal roles in transducing developmental cues and environmental signals into cellular responses through pathways initiated by MAPK kinase kinases (MAP3K). AtYODA is a MAP3K of Arabidopsis thaliana that controls stomatal development and non-canonical immune responses. Arabidopsis plants overexpressing a constitutively active YODA protein (AtCA-YDA) show broad-spectrum disease resistance and constitutive expression of defensive genes. We tested YDA function in crops immunity by heterologously overexpressing AtCA-YDA in Solanum lycopersicum. We found that these tomato AtCA-YDA plants do not show developmental phenotypes and fitness alterations, except a reduction in stomatal index, as reported in Arabidopsis AtCA-YDA plants. Notably, AtCA-YDA tomato plants show enhanced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and constitutive upregulation of defense-associated genes, corroborating the functionality of YDA in tomato immunity. This function was further supported by generating CRISPR/Cas9-edited tomato mutants impaired in the closest orthologs of AtYDA [Solyc08g081210 (SlYDA1) and Solyc03g025360 (SlYDA2)]. Slyda1 and Slyda2 mutants are highly susceptible to P. syringae pv. tomato DC3000 in comparison to wild-type plants but only Slyda2 shows altered stomatal index. These results indicate that tomato orthologs have specialized functions and support that YDA also regulates immune responses in tomato and may be a trait for breeding disease resistance.

The formation of hair follicles, a landmark of mammals, requires complex mesenchymal–epithelial interactions and it is commonly believed that embryonic epidermal cells are the only cells that can respond to hair follicle morphogenetic signals in vivo. Here, we demonstrate that epithelial stem cells of non-skin origin (e.g. that of cornea, oesophagus, vagina, bladder, prostate) that express the transcription factor Tp63, a master gene for the development of epidermis and its appendages, can respond to skin morphogenetic signals. When exposed to a newborn skin microenvironment, these cells express hair-follicle lineage markers and contribute to hair follicles, sebaceous glands and/or epidermis renewal. Our results demonstrate that lineage restriction is not immutable and support the notion that all Tp63-expressing epithelial stem cells, independently of their embryonic origin, have latent skin competence explaining why aberrant hair follicles or sebaceous glands are sometimes observed in non-skin tissues (e.g. in cornea, vagina or thymus).

Purpose The exact cellular types that form the human fovea remain a subject of debate, and few studies have been conducted on human macula to solve this question. The purpose of this study was to perform immunohistochemistry on fresh human samples to characterize the glial cells that form the human fovea. Methods Immunohistochemistry was performed using antibodies against proteins expressed in astrocytes or in retinal Müller glial cells or both types of cells on six human macula obtained from eyes enucleated for peripheral intraocular tumors and on two postmortem eyes from healthy donors. The posterior poles of the enucleated eyes were cryosectioned and stained with antibodies against the glial proteins GFAP, vimentin, CRALBP, glutamine synthetase, and connexin 43. Results A population of cells positive for GFAP and negative for glutamine synthetase and CRALBP that express connexin 43 were identified at the roof of the foveal pit. These cells are distinct from the Müller cone cells described by Yamada and Gass, suggesting that another type of foveal glial cells, most likely astrocytes, are present in the human fovea. Conclusions This study showed that in humans, astrocytic glial cells cover the foveal pit. Their roles in macula homeostasis and mechanisms of macular disease remain to be determined.

Purposewas to create an in vitro model of human retinal detachment (RD) to study the mechanisms of photoreceptor death.MethodsHuman retinas were obtained through eye globe donations for research purposes and cultivated as explants. Cell death was investigated in retinas with (control) and without retinal pigment epithelium (RPE) cells to mimic RD. Tissues were studied at different time points and immunohistological analyses for TUNEL, Cleaved caspase3, AIF, CDK4 and the epigenetic mark H3K27me3 were performed. Human and monkey eye globes with retinal detachment served as controls.ResultsThe number of TUNEL-positive cells, compared between 1 and 7 days, increased with time in both retinas with RPE (from 1.2 ± 0.46 to 8 ± 0.89, n = 4) and without RPE (from 2.6 ± 0.73 to 16.3 ± 1.27, p < 0.014). In the group without RPE, cell death peaked at day 3 (p = 0.014) and was high until day 7. Almost no Cleaved-Caspase3 signal was observed, whereas a transient augmentation at day 3 of AIF-positive cells was observed to be about 10-fold in comparison to the control group (n = 2). Few CDK4-positive cells were found in both groups, but significantly more in the RD group at day 7 (1.8 ± 0.24 vs. 4.7 ± 0.58, p = 0.014). The H3K27me3 mark increased by 7-fold after 5 days in the RD group (p = 0.014) and slightly decreased at day 7 and was also observed to be markedly increased in human and monkey detached retina samples.ConclusionAIF expression coincides with the first peak of cell death, whereas the H3K27me3 mark increases during the cell death plateau, suggesting that photoreceptor death is induced by different successive pathways after RD. This in vitro model should permit the identification of neuroprotective drugs with clinical relevance.

Conjunctival melanoma (CJM) is a rare but potentially lethal and highly-recurrent cancer of the eye. Similar to cutaneous melanoma (CM), it originates from melanocytes. Unlike CM, however, CJM is relatively poorly characterized from a genomic point of view. To fill this knowledge gap and gain insight into the genomic nature of CJM, we performed whole-exome (WES) or whole-genome sequencing (WGS) of tumor-normal tissue pairs in 14 affected individuals, as well as RNA sequencing in a subset of 11 tumor tissues. Our results show that, similarly to CM, CJM is also characterized by a very high mutation load, composed of approximately 500 somatic mutations in exonic regions. This, as well as the presence of a UV light-induced mutational signature, are clear signs of the role of sunlight in CJM tumorigenesis. In addition, the genomic classification of CM proposed by TCGA seems to be well-applicable to CJM, with the presence of four typical subclasses defined on the basis of the most frequently mutated genes: BRAF , NF1 , RAS , and triple wild-type. In line with these results, transcriptomic analyses revealed similarities with CM as well, namely the presence of a transcriptomic subtype enriched for immune genes and a subtype enriched for genes associated with keratins and epithelial functions. Finally, in seven tumors we detected somatic mutations in ACSS3 , a possible new candidate oncogene. Transfected conjunctival melanoma cells overexpressing mutant ACSS3 showed higher proliferative activity, supporting the direct involvement of this gene in the tumorigenesis of CJM. Altogether, our results provide the first unbiased and complete genomic and transcriptomic classification of CJM.

Purpose: To assess the role of the canonical Wnt pathway via activation of β-catenin in tumor progression of conjunctival melanoma. Methods: β-Catenin localization was assessed by immunohistochemistry in 43 conjunctival nevi, 48 primary acquired melanoses (PAM; conjunctival melanocytic intraepithelial neoplasia), and 44 conjunctival melanomas. Activation of the canonical or the noncanonical Wnt pathway was tested in vitro in 4 conjunctival melanoma cell lines with stimulation of either Wnt5a or Wnt3a. Wound healing assays were performed with Wnt5a. Results: Nuclear β-catenin expression was found in 16% of the nevi, in 15% of the melanomas, and in 4% of the PAM. Membranous β-catenin expression was identified in all the nevi and PAM and in 97.7% of the melanomas. In vitro, Wnt5a stimulation in the 4 conjunctival melanomas and in 1 skin melanoma cell line did not induce nuclear translocation of β-catenin, nor did it increase cell motility in the wound healing assays. Wnt3a stimulation did not induce nuclear localization of β-catenin in any of the cell lines tested. Conclusions: In conjunctival melanoma, nuclear localization and activation of β-catenin appear to be limited, suggesting that inhibition of ARF6, responsible for β-catenin activation, in subsets of skin melanoma may not represent a treatment option for this tumor. In vitro, Wnt3a or Wnt5a did not induce nuclear β-catenin localization.

Purpose: To assess the role of the canonical Wnt pathway via activation of β-catenin in tumor progression of conjunctival melanoma. Methods: β-Catenin localization was assessed by immunohistochemistry in 43 conjunctival nevi, 48 primary acquired melanoses (PAM; conjunctival melanocytic intraepithelial neoplasia), and 44 conjunctival melanomas. Activation of the canonical or the noncanonical Wnt pathway was tested in vitro in 4 conjunctival melanoma cell lines with stimulation of either Wnt5a or Wnt3a. Wound healing assays were performed with Wnt5a. Results: Nuclear β-catenin expression was found in 16% of the nevi, in 15% of the melanomas, and in 4% of the PAM. Membranous β-catenin expression was identified in all the nevi and PAM and in 97.7% of the melanomas. In vitro, Wnt5a stimulation in the 4 conjunctival melanomas and in 1 skin melanoma cell line did not induce nuclear translocation of β-catenin, nor did it increase cell motility in the wound healing assays. Wnt3a stimulation did not induce nuclear localization of β-catenin in any of the cell lines tested. Conclusions: In conjunctival melanoma, nuclear localization and activation of β-catenin appear to be limited, suggesting that inhibition of ARF6, responsible for β-catenin activation, in subsets of skin melanoma may not represent a treatment option for this tumor. In vitro, Wnt3a or Wnt5a did not induce nuclear β-catenin localization.

Shoot branching is a major determinant of plant architecture and is regulated by both endogenous and environmental factors. BRANCHED1 (BRC1) is a central local regulator that integrates signals controlling shoot branching. So far, the regulation of BRC1 activity at the protein level is still largely unknown. In this study, we demonstrated that TIE1 (TCP interactor containing EAR motif protein 1), a repressor previously identified as an important factor in the control of leaf development, also regulates shoot branching by repressing BRC1 activity. TIE1 is predominantly expressed in young axillary buds. The gain-of-function mutant tie1-D produced more branches and the overexpression of TIE1 recapitulated the increased branching of tie1-D, while disruption of TIE1 resulted in lower bud activity and fewer branches. We also demonstrated that the TIE1 protein interacts with BRC1 in vitro and in vivo. Expression of BRC1 fused with the C-terminus of the TIE1 protein in wild type caused excessive branching similar to that observed in tie1-D and brc1 loss-of-function mutants. Transcriptome analyses revealed that TIE1 regulated about 30% of the BRC1-dependent genes, including the BRC1 direct targets HB21, HB40 and HB53. These results indicate that TIE1 acts as a positive regulator of shoot branching by directly repressing BRC1 activity. Thus, our results reveal that TIE1 is an important shoot branching regulator, and provide new insights in the post-transcriptional regulation of the TCP transcription factor BRC1.