The YABBY gene SHATTERING1 controls activation rather than patterning of the abscission zone in Setaria viridis

Abstract

Summary Abscission is predetermined in specialized cell layers called the abscission zone (AZ) and activated by developmental or environmental signals. In the grass family, most identified AZ genes regulate AZ anatomy, which differs among lineages. A YABBY transcription factor, SHATTERING1 (SH1), is a domestication gene regulating abscission in multiple cereals, including rice and Setaria. In rice, SH1 inhibits lignification specifically in the AZ. However, the AZ of Setaria is nonlignified throughout, raising the question of how SH1 functions in species without lignification. Crispr‐Cas9 knockout mutants of SH1 were generated in Setaria viridis and characterized with histology, cell wall and auxin immunofluorescence, transmission electron microscopy, hormonal treatment and RNA‐Seq analysis. The sh1 mutant lacks shattering, as expected. No differences in cell anatomy or cell wall components including lignin were observed between sh1 and the wild‐type (WT) until abscission occurs. Chloroplasts degenerated in the AZ of WT before abscission, but degeneration was suppressed by auxin treatment. Auxin distribution and expression of auxin‐related genes differed between WT and sh1, with the signal of an antibody to auxin detected in the sh1 chloroplast. SH1 in Setaria is required for activation of abscission through auxin signaling, which is not reported in other grass species.

Dior R. Kelley

“…This study nicely showed how local auxin metabolism can impact de novo organ formation. There was also a very cool study on a new role for auxin signaling in shattering, in Setaria, which has not been observed in other grass species (Yu et al, 2023). I also enjoy reading New Phytologist for its excellent science in nonmodel plants.…”

Molecular Characterization and Expression Analysis of YABBY Genes in Chenopodium quinoa

“…In addition, these genes are responsible for maintaining the proper activity of the meristem [31,36]. YABBYs were also found in rice, maize, and wheat [37][38][39][40] and found functioning in carpel specification and leaf midrib formation [41], the development of vasculature [42], the determination of the fate of abaxial cells in leaf development and architecture [43][44][45], lateral organ development and meristem maintenance in spikelet [46][47][48], seed shattering [49,50], and the regulation of gibberellin metabolism [51]. Recently, a few studies have shown that YABBY genes are involved in abiotic stress responses, such as salt and drought stresses [52,53], cadmium (Cd) stress [54], and cold and heat stresses [55].…”