E3 ligases MAC3A and MAC3B ubiquitinate UBIQUITIN-SPECIFIC PROTEASE14 to regulate organ size in Arabidopsis.

The molecular mechanisms controlling organ size during plant development ultimately influence crop yield. However, a deep understanding of these mechanisms is still lacking. UBIQUITIN-SPECIFIC PROTEASE14 (UBP14), encoded by DA3, is an essential factor determining organ size in Arabidopsis (Arabidopsis thaliana). Here, we identified two suppressors of the da3-1 mutant phenotype, namely SUPPRESSOR OF da3-1 1 and 2 (SUD1 and SUD2), which encode the E3 ligases MOS4-ASSOCIATED COMPLEX 3A (MAC3A) and MAC3B, respectively. The mac3a-1 and mac3b-1 mutations partially suppressed the high ploidy level and organ size phenotypes observed in the da3-1 mutant. Biochemical analysis showed that MAC3A and MAC3B physically interacted with and ubiquitinated UBP14/DA3 to modulate its stability. We previously reported that UBP14/DA3 acts upstream of the B-type cyclin-dependent kinase CDKB1;1 and maintains its stability to inhibit endoreduplication and cell growth. In this work, MAC3A and MAC3B were found to promote the degradation of CDKB1;1 by ubiquitinating UBP14/DA3. Genetic analysis suggests that MAC3A and MAC3B act in a common pathway with UBP14/DA3 to control endoreduplication and organ size. Thus, our findings define a regulatory module, MAC3A/MAC3B-UBP14-CDKB1;1, that plays a critical role in determining organ size and endoreduplication in Arabidopsis. © The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists.

Citation

Xiaopeng Guo, Xin Zhang, Shan Jiang, Xin Qiao, Bolun Meng, Xiaohang Wang, Yanan Wang, Kaihuan Yang, Yilan Zhang, Na Li, Tianyan Chen, Yiyang Kang, Mengyi Yao, Xuan Zhang, Xinru Wang, Erling Zhang, Junhua Li, Dawei Yan, Zhubing Hu, José Ramón Botella, Chun-Peng Song, Yunhai Li, Siyi Guo. E3 ligases MAC3A and MAC3B ubiquitinate UBIQUITIN-SPECIFIC PROTEASE14 to regulate organ size in Arabidopsis. Plant physiology. 2024 Jan 31;194(2):684-697

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PMID: 37850874

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