AUTHOR=Huang Tongtong , Zhang Heng , Zhou Yiming , Su Yanhua , Zheng Han , Ding Yong 

TITLE=Phosphorylation of Histone H2A at Serine 95 Is Essential for Flowering Time and Development in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.761008

DOI=10.3389/fpls.2021.761008

ISSN=1664-462X

ABSTRACT=<p>Phosphorylation of H2A at serine 95 (H2AS95ph) mediated by MLK4 promotes flowering and H2A.Z deposition. However, little is known about MLK1, MLK2, and MLK3 during the flowering time. Here, we systemically analyze the functions of MLK family in flowering time and development. Mutation in <italic>MLK3</italic>, but not <italic>MLK1</italic> and <italic>MLK2</italic>, displayed late-flowering phenotype. Loss of <italic>MLK3</italic> function enhanced the late-flowering phenotype of <italic>mlk4</italic> mutant, but not reinforced the late-flowering phenotype of <italic>mlk1 mlk2</italic> double mutants. MLK3 displayed the kinase activity to histone H2AS95ph <italic>in vitro</italic>. The global H2AS95ph levels were reduced in <italic>mlk3 mlk4</italic>, but not in <italic>mlk3</italic> and <italic>mlk4</italic> single mutant and <italic>mlk1 mlk2</italic> double mutant, and the H2AS95ph levels in <italic>mlk1 mlk3 mlk4</italic> and <italic>mlk2 mlk3 mlk4</italic> were similar to those in <italic>mlk3 mlk4</italic> double mutant. MLK3 interacted with CCA1, which binds to the promoter of <italic>GI</italic>. Correspondingly, the transcription levels and H2AS95ph levels of <italic>GI</italic> were reduced in <italic>mlk3</italic> and <italic>mlk4</italic> single mutant, and greatly decreased in <italic>mlk3 mlk4</italic> double mutant, but not further attenuated in <italic>mlk1 mlk3 mlk4</italic> and <italic>mlk2 mlk3 mlk4</italic> triple mutant. Together, our results suggested that H2AS95ph deposition mediated by MLK3 and MLK4 is essential for flowering time in <italic>Arabidopsis</italic>.</p>