The Phylogeny of Brassicaceae YABBYs and the CRC-Mediated Regulation of Stigma Development in Brassica napus

The YABBY family consists of plant-specific transcription factors that regulate organ polarity and reproductive development. As a member of this family, CRABS CLAW (CRC) plays crucial roles, but its molecular mechanism in oilseed rape stigma development remains unclear. In this study, we identified YABBY genes in four Brassicaceae species. The results showed that CRC proteins are highly conserved in structure, but their cis-acting elements vary among species. To explore its function, we performed transcriptome sequencing on an oilseed rape CRC-deficient mutant (sd). The transcriptome data revealed multiple changes in the sd mutant. Specifically, brassinosteroid (BR) signaling factors were downregulated. Sugar transporters and auxin-related genes showed abnormal expression. Furthermore, pro-senescence and programmed cell death (PCD) genes were upregulated, whereas the classic senescence pathway remained unchanged. Based on these findings, we propose a potential mechanism. The loss of CRC disrupts BR signaling, sugar transport, and calcium homeostasis. This disruption triggers non-classic death of stigma papilla cells, which hinders pollen tube penetration and reduces seed set. Notably, increasing environmental humidity partially rescued the seed set, likely by delaying cell death. Although these transcriptomic insights warrant further experimental validation, this study provides valuable clues and genetic resources for future research on reproductive development in oilseed rape.