MxMPK6‐2‐mediated phosphorylation enhances the response of apple rootstocks to Fe deficiency by activating PM H+‐ATPase MxHA2
MxMPK6‐2‐mediated phosphorylation enhances the response of apple rootstocks to Fe deficiency by activating PM H+‐ATPase MxHA2
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DOI：
10.1111/tpj.16360
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Yi Wang
中科院分区：
文献类型：
--
作者：
Qiran Sun;Danrui Zhao;Min Gao;Yue Wu;Longmei Zhai;Shan Sun;Ting Wu;Xinzhong Zhang;Xuefeng Xu;Zhenhai Han;Yi Wang
Iron (Fe) deficiency significantly affects the growth and development, fruit yield, and quality of apples. Apple roots respond to Fe deficiency stress by promoting H+ secretion, which acidifies the soil. In this study, the plasma membrane (PM) H+ -ATPase MxHA2 promoted H+ secretion and root acidification of apple rootstocks under Fe deficiency stress. H+ -ATPase MxHA2 is up-regulated in Fe-efficient apple rootstock of Malus xiaojinensis at the transcription level. Fe deficiency also induced kinase MxMPK6-2, a positive regulator in Fe absorption that can interact with MxHA2. However, the mechanism involving these two factors under Fe deficiency stress is unclear. MxMPK6-2 overexpression in apple roots positively regulated PM H+ -ATPase activity, thus enhancing root acidification under Fe deficiency stress. Moreover, co-expression of MxMPK6-2 and MxHA2 in apple rootstocks further enhanced PM H+ -ATPase activity under Fe deficiency. MxMPK6-2 phosphorylated MxHA2 at the Ser909 site of C terminus, Thr320, and Thr412 sites of the Central loop region. Phosphorylation at the Ser909 and Thr320 promoted PM H+ -ATPase activity, while phosphorylation at Thr412 inhibited PM H+ -ATPase activity. MxMPK6-2 also phosphorylated the Fe deficiency-induced transcription factor MxbHLH104 at the Ser169 site, which then could bind to the promoter of MxHA2, thus enhancing MxHA2 upregulation. In conclusion, the MAP kinase MxMPK6-2-mediated phosphorylation directly and indirectly regulates PM H+ -ATPase MxHA2 activity at the protein post-translation and transcription levels, thus synergistically enhancing root acidification under Fe deficiency stress.
