STERILE APETALA modulates the stability of a repressor protein complex to control organ size in Arabidopsis thaliana

Organ size control is of particular importance for developmental biology and agriculture, but the mechanisms underlying organ size regulation remain elusive in plants. Meristemoids, which possess stem cell-like properties, have been recognized to play important roles in leaf growth. We have recently reported that the Arabidopsis F-box protein STERILE APETALA (SAP)/SUPPRESSOR OF DA1 (SOD3) promotes meristemoid proliferation (增殖) and regulates organ size by influencing the stability of the transcriptional regulators PEAPODs (PPDs). Here we demonstrate that KIX8 and KIX9, which function as adaptors for the corepressor (辅阻遏子) TOPLESS and PPD, are novel substrates of SAP. SAP interacts with KIX8/9 and modulates their protein stability. Further results show that SAP acts in a common pathway with KIX8/9 and PPD to control organ growth by regulating meristemoid cell proliferation. Thus, these findings reveal a molecular mechanism by which SAP targets the KIX-PPD repressor complex for degradation to regulate meristemoid cell proliferation and organ size.

植物器官大小对于发育生物学以及农作物的研究是尤其重要的，但有关控制植物器官大小的分子机制还处于比较模糊的阶段。Meristemoids，一类有着类似于干细胞特性的细胞，被认为在植物叶片的生长中发挥重要作用。本文作者曾报道过拟南芥的F-box蛋白SAP/SOD3通过影像转录调控子PPDs的稳定性促进meristemoid的增殖、调控器官大小。本文报道了KIX8和KIX9作为辅阻遏子TOPLESS和PPD的接头分子，是SAP新发现的低物。SAP与KIX8/9互作，并调控其蛋白稳定性。进一步的研究显示SAP与KIX8/9、PPD一道发挥作用，通过调控meristemoid细胞增殖来控制器官的大小。因此，本文的发现揭示了SAP通过靶向KIX-PPD降解抑制复合物进而调控meristemoid细胞增殖和器官大小。

p.s. Meristemoids: A small, triangular stomatal precursor cell that functions temporarily as a stem cell in a meristem. (wiktionary)

个人简介：1996年，河南大学，学士；1999年，中国农业科学院，硕士；2003年，中国科学院遗传与发育生物学研究所，博士；2003-2008年，英国John Innes Centre，博士后；2008年，中国科学院遗传与发育生物学研究所，研究员，博士生导师。

doi: https://doi.org/10.1371/journal.pgen.1007218