Pengcheng Zhao

The seedless trait in grapes primarily arises from pseudo-parthenocarpy, driven by early seed abortion involving programmed cell death (PCD) and autophagy. However, the specific regulatory networks governing these pathways remain poorly defined. To address this, we systematically characterized the PCD-related (vacuolar processing enzyme [VPE] and metacaspase [MC]) and autophagy-related (ATG) gene families in the seedless cultivar ‘Jingkejing’ utilizing comprehensive bioinformatic analyses, spatiotemporal transcriptomic profiling, and transient expression assays. We identified three VPE, six MC, and 33 ATG genes, whose promoters were significantly enriched in hormone-responsive and transcription factor (TF)-binding motifs. Transcriptomic profiling across critical seed abortion stages highlighted VvγVPE and VvMC9 as key differentially expressed genes. Furthermore, protein–protein interaction predictions indicated extensive crosstalk among PCD/ATG proteins, kinases, and ubiquitin system components. Notably, transient expression assays confirmed that two core transcription factors, VvWRKY46 and VvERF71, specifically regulate downstream PCD-related targets, supporting a proposed multi-hormonal and TF-mediated regulatory network during seed abortion. These findings elucidate the molecular mechanisms underlying pseudo-parthenocarpy, providing essential candidate gene resources for the marker-assisted breeding of seedless grapes.

Ethylene is one crucial phytohormone modulating plants’ organ development and ripening process, especially in fruits, but its action modes and discrepancies in non-climacteric grape and climacteric peach in these processes remain elusive. This work is focused on the action mode divergences of ethylene during the modulation of the organ development and ripening process in climacteric/non-climacteric plants. We characterized the key enzyme genes in the ethylene synthesis pathway, VvACO1 and PpACO1, and uncovered that their sequence structures are highly conserved, although their promoters exhibit important divergences in the numbers and types of the cis-elements responsive to hormones, implying various responses to hormone signals. Subsequently, we found the two have similar expression modes in vegetative organ development but inverse patterns in reproductive ones, especially in fruits. Then, VvACO1 and PpACO1 were further validated in promoting fruit ripening functions through their transient over-expression/RNAi-expression in tomatoes, of which the former possesses a weaker role than the latter in the fruit ripening process. Our findings illuminated the divergence in the action patterns and function traits of the key VvACO1/PpACO1 genes in the tissue development of climacteric/non-climacteric plants, and they have implications for further gaining insight into the interaction mechanism of ethylene signaling during the modulation of the organ development and ripening process in climacteric/non-climacteric plants.

Calmodulin-like proteins (CMLs) are calcium (Ca²⁺) sensors involved in plant growth and development as well as adaptation to environmental stresses; however, their roles in plant responses to cold are not well understood. To reveal the role of MsCML10 from alfalfa (Medicago sativa) in regulating cold tolerance, we examined transgenic alfalfa and Medicago truncatula overexpressing MsCML10, MsCML10-RNAi alfalfa, and a M. truncatula cml10-1 mutant and identified MsCML10-interacting proteins. MsCML10 and MtCML10 transcripts were induced by cold treatment. Upregulation or downregulation of MsCML10 resulted in increased or decreased cold tolerance, respectively, while cml10-1 showed decreased cold tolerance that was complemented by expressing MsCML10, suggesting that MsCML10 regulates cold tolerance. MsCML10 interacted with glutathione S-transferase (MsGSTU8) and fructose 1,6-biphosphate aldolase (MsFBA6), and the interaction depended on the presence of Ca²⁺. The altered activities of Glutathione S-transferase and FBA and levels of ROS and sugars were associated with MsCML10 transcript levels. We propose that MsCML10 decodes the cold-induced Ca²⁺ signal and regulates cold tolerance through activating MsGSTU8 and MsFBA6, leading to improved maintenance of ROS homeostasis and increased accumulation of sugars for osmoregulation, respectively.