Dissecting promoter of InMYB1 gene showing petal-specific expression

Petal abscission is promoted by jasmonic acid-induced autophagy at Arabidopsis petal bases

In angiosperms, the transition from floral-organ maintenance to abscission determines reproductive success and seed dispersion. For petal abscission, cell-fate decisions specifically at the petal-cell base are more important than organ-level senescence or cell death in petals. However, how this transition is regulated remains unclear. Here, we identify a jasmonic acid (JA)-regulated chromatin-state switch at the base of Arabidopsis petals that directs local cell-fate determination via autophagy. During petal maintenance, co-repressors of JA signaling accumulate at the base of petals to block MYC activity, leading to lower levels of ROS. JA acts as an airborne signaling molecule transmitted from stamens to petals, accumulating primarily in petal bases to trigger chromatin remodeling. This allows MYC transcription factors to promote chromatin accessibility for downstream targets, including NAC DOMAIN-CONTAINING PROTEIN102 (ANAC102). ANAC102 accumulates specifically at the petal base prior to abscission and triggers ROS accumulation and cell death via AUTOPHAGY-RELATED GENEs induction. Developmentally induced autophagy at the petal base causes maturation, vacuolar delivery, and breakdown of autophagosomes for terminal cell differentiation. Dynamic changes in vesicles and cytoplasmic components in the vacuole occur in many plants, suggesting JA-NAC-mediated local cell-fate determination by autophagy may be conserved in angiosperms.

Genome-wide analysis of R2R3-MYB transcription factors in Japanese morning glory

The R2R3-MYB transcription factor is one of the largest transcription factor families in plants. R2R3-MYBs play a variety of functions in plants, such as cell fate determination, organ and tissue differentiations, primary and secondary metabolisms, stress and defense responses and other physiological processes. The Japanese morning glory (Ipomoea nil) has been widely used as a model plant for flowering and morphological studies. In the present study, 127 R2R3-MYB genes were identified in the Japanese morning glory genome. Information, including gene structure, protein motif, chromosomal location and gene expression, were assigned to the InR2R3-MYBs. Phylogenetic tree analysis revealed that the 127 InR2R3-MYBs were classified into 29 subfamilies (C1-C29). Herein, physiological functions of the InR2R3-MYBs are discussed based on the functions of their Arabidopsis orthologues. InR2R3-MYBs in C9, C15, C16 or C28 may regulate cell division, flavonol biosynthesis, anthocyanin biosynthesis or response to abiotic stress, respectively. C16 harbors the known anthocyanin biosynthesis regulator, InMYB1 (INIL00g10723), and putative anthocyanin biosynthesis regulators, InMYB2 (INIL05g09650) and InMYB3 (INIL05g09651). In addition, INIL05g09649, INIL11g40874 and INIL11g40875 in C16 were suggested as novel anthocyanin biosynthesis regulators. We organized the R2R3-MYB transcription factors in the morning glory genome and assigned information to gene and protein structures and presuming their functions. Our study is expected to facilitate future research on R2R3-MYB transcription factors in Japanese morning glory.