Coordination of lignin and pectin remodeling by a NAC transcription factor regulates seed abscission in sesame (Sesamum indicum L.)

Title : Coordination of lignin and pectin remodeling by a NAC transcription factor regulates seed abscission in sesame (Sesamum indicum L.)

Abstract:

Seed shattering, an adaptation that enables seeds to disperse over a wide area, is essential for plant reproduction. However, in agriculture it poses a major challenge, since for crops such as sesame (Sesamum indicum L) it causes grain loss during harvest. Shattering typically occurs via capsule dehiscence and seed abscission from the placenta, either simultaneously or independently depending on the species. In this study, we reveal a novel cell wall-associated mechanism that underlies seed abscission in sesame cultivar Suwon195 (SW195), which exhibits delayed seed abscission relative to the easy-shattering IT030100 cultivar. Histological and transcriptome analyses revealed that cell wall remodeling, especially involving pectin and lignin, contributes to the delayed abscission phenotype of SW195. Specifically, we found that in SW195 higher expression and activity of pectin-modifying enzymes led to reduced methyl-esterification and increased cell wall rigidity in the abscission zone (AZ), suggesting that regulation of pectin esterification is a critical factor seed abscission. Moreover, lignification in the AZ was weaker in SW195 and was associated with the regulation of pectin-modifying enzymes. QTL mapping and whole-genome resequencing identified a major QTL on chromosome 9 that contained two genes: a NAC transcription factor (SiNAC, SIN_1025412) and a pectin methylesterase inhibitor (SiPMEI, SIN_1025380). Transient overexpression of SiNAC in sesame consistently enhanced lignin biosynthesis. Overall, these findings demonstrate that coordinated regulation of lignin biosynthesis and pectin remodeling is essential for seed abscission in sesame, and that SiNAC acts as a central regulator.

Biography:

I am a postdoctoral fellow at the Research Institute of Basic Sciences, Seoul National University. I received my Ph.D. in Biology from Chungbuk National University, where I studied the roles of brassinosteroids in drought tolerance and xylem development in tomato (Solanum lycopersicum). My current research focuses on molecular mechanisms regulating organ abscission in plants and the hormone signaling networks that control plant development and stress responses. I aim to elucidate key signaling and transcriptional pathways that coordinate cell separation and environmental adaptation in plants.