Phosphorylation of Serine 186 of bHLH Transcription Factor SPEECHLESS Promotes Stomatal Development in Arabidopsis

• Published in: Molecular plant 2015-05, Vol.8 (5), p.783-795
• Main Authors: Yang, Ke-Zhen, Jiang, Min, Wang, Ming, Xue, Shan, Zhu, Ling-Ling, Wang, Hong-Zhe, Zou, Jun-Jie, Lee, Eun-Kyoung, Sack, Fred, Le, Jie
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Arabidopsis; Arabidopsis - chemistry; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Basic Helix-Loop-Helix Transcription Factors - chemistry; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; development; Gene Expression Regulation, Plant; Phosphorylation; Plant Stomata - chemistry; Plant Stomata - genetics; Plant Stomata - growth & development; Plant Stomata - metabolism; Serine - chemistry; Serine - genetics; Serine - metabolism; stomata; transcription factor; 丝氨酸; 促分裂原活化蛋白激酶; 化促; 拟南芥; 磷酸化; 细胞周期蛋白依赖性激酶; 转录因子; 进气孔
• ISSN: 1674-2052; 1752-9867
• DOI: 10.1016/j.molp.2014.12.014

The initiation of stomatal lineage and subsequent asymmetric divisions in Arabidopsis require the activity of the basic helix-loop-helix transcription factor SPEECHLESS （SPCH）. It has been shown that SPCH controls entry into the stomatal lineage as a substrate either of the MITOGEN-ACTIVATED PROTEIN KINASE （MAPK） cascade or GSK3-1ike kinase BRASSlNOSTEROID INSENSITIVE 2 （BIN2）. Here we show that three serine residues of SPCH appear to be the primary phosphorylation targets of Cyclin-Dependent Kinases A;1 （CDKA;1） in vitro, and among them Serine 186 plays a crucial role in stomatal formation. Expression of an SPCH construct harboring a mutation that results in phosphorylation deficiencies on Serine 186 residue failed to rescue stomatal defects in spch null mutants. Expression of a phosphorylation-mimic mutant SPCHS186D complemented stomatal production defects in the transgenic lines harboring the targeted expression of dominant-negative CDKA;1.N146. Therefore, in addition to MAPK- and BIN2-mediated phos- phorylation on SPCH, phosphorylation at Serine 186 is positively required for SPCH function in regulating stomatal development.