Cell proliferation suppressor RBR1 interacts with ARID1 to promote pollen mitosis via stabilizing DUO1 in Arabidopsis

Abstract

• In plants, sperm cell formation involves two rounds of pollen mitoses, in which the microspore initiates the first pollen mitosis (PMI) to produce a vegetative cell and a generative cell, then the generative cell continues the second mitosis (PMII) to produce two sperm cells. DUO1, a R2R3 Myb transcription factor, is activated in the generative cell to promote S-G2/M transition during PMII. Loss-of-function of DUO1 caused a complete arrest of PMII. Despite the importance of DUO1, how DUO1 is regulated is largely unexplored.
• We previously demonstrated that ARID1, an ARID transcription factor, stimulates DUO1 transcription.
• Here, we show that cell proliferation suppressor RBR1 interacts with ARID1 to stabilize DUO1. While the C-terminus of RBR1 is dispensable for vegetative growth, it plays a crucial role in reproductive development and facilitates interaction with ARID1. Moreover, DUO1 is a short-lived protein, ARID1 promotes the RBR1–DUO1 interaction, and RBR1 stabilizes DUO1 in a proteasome-dependent manner. Thus, RBR1 promotes DUO1-dependent PMII progression via antagonizing its repressive role in the cell cycle factors CDKA;1 and CYCB1;1.
• Collectively, we uncover that ARID1 and RBR1 act in concert to regulate DUO1 at both the transcriptional and posttranscriptional levels, balancing cell specification and cell division.