CIPK11-Dependent Phosphorylation Modulates FIT Activity to Promote Arabidopsis Iron Acquisition in Response to Calcium Signaling

First author: Regina Gratz; Affiliations: Heinrich-Heine University (海因里希-海因大学): Düsseldorf, Germany

Corresponding author: Petra Bauer

Nutrient acquisition is entangled with growth and stress in sessile organisms. The bHLH transcription factor FIT is a key regulator of Arabidopsis iron (Fe) acquisition and post-translationally activated upon low Fe. We identified CBL-INTERACTING PROTEIN KINASE CIPK11 as a FIT interactor. Cytosolic Ca2+ concentration and CIPK11 expression are induced by Fe deficiency. cipk11 mutant plants display compromised root Fe mobilization and seed Fe content. Fe uptake is dependent on CBL1/CBL9. CIPK11 phosphorylates FIT at Ser272, and mutation of this target site modulates FIT nuclear accumulation, homo-dimerization, interaction with bHLH039, and transcriptional activity and affects the plant’s Fe-uptake ability. We propose that Ca2+-triggered CBL1/9-mediated activation of CIPK11 and subsequent phosphorylation of FIT shifts inactive into active FIT, allowing regulatory protein interactions in the nucleus. This biochemical link between Fe deficiency and the cellular Ca2+ decoding machinery represents an environment-sensing mechanism to adjust nutrient uptake.

固着生物的营养获取与生长和胁迫息息相关。bHLH转录因子FIT是拟南芥Fe获取的关键调控因子，在植物低铁是被翻译后激活。本文中，作者鉴定了CIPK11与FIT相互作用。植物缺铁会诱导胞质Ca2+浓度和CIPK11基因的表达。cipk11突变体植株会显示出根可利用铁和种子铁含量的缺陷。铁吸收依赖于CBL1/CBL9。CIPK11磷酸化FIT272号氨基酸Ser，该位点的突变会改变FIT在核中的积累、同源二聚化、与bHLH039的互作以及转录活性，进而影响植物吸收铁的能力。作者假设Ca2+诱导的CBL1/9介导的CIPK11激活以及随后的FIT磷酸化将FIT转变为活性FIT，使得其能够在核中与靶蛋白发生互作，起到调控植物铁吸收的作用。本文所报道的铁缺陷与细胞内Ca2+信号之间的生化关联代表了植物适应营养吸收演化出的一种感应外界环境的机制。

通讯：Petra Bauer (http://www.botanik.hhu.de/en/head-of-institute/vita.html)

个人简介：1986-1992年，科隆大学，学士；1995年，科隆大学，博士。

doi: https://doi.org/10.1016/j.devcel.2019.01.006

Journal: Developmental Cell

First Published: January 31, 2019