Plant IONIC CURRENT FAMILY A proteins boost stress tolerance via calcium uptake

Calcium (Ca²⁺) is an essential macronutrient for plant growth and defense, yet the molecular mechanisms regulating its uptake from soil remain largely undefined. Through bioinformatics and electrophysiological screening, we identified a group of plant-specific proteins, named the IONIC CURRENT FAMILY A (ICAs), which confer Ca²⁺-permeable nonselective cation channel (CNCC) activities in heterologous systems. In Arabidopsis thaliana,ICA1,ICA2,ICA3, and ICA4 are predominantly expressed in root cells and localized to the plasma membrane. Under both limited and excessive external Ca²⁺ conditions,ica1/2/3/4quadruple mutants display hypersensitivity or reduced sensitivity, respectively, as evidenced by altered root length. Additionally, these mutants show increased sensitivity to various abiotic and biotic stresses under normal Ca²⁺ conditions. The ica mutants lack the previously characterized CNCC-mediated currents in roots that facilitate Ca2+uptake, resulting in lower calcium levels and altered gene expression profiles compared to wild-type (WT) plants. Our findings suggest that AtICA1/2/3/4 may function as components of CNCCs, mediating Ca²⁺ uptake crucial for root morphogenesis under suboptimal Ca²⁺ conditions and broad environmental stress tolerance under optimal Ca²⁺ conditions. This study addresses a significant gap in understanding nutrient uptake mechanisms and has implications for developing stress-resilient crops and calcium-rich food sources.

Zhijie Ren, Jinghui Cui, Tianqi Wang, Jie Wen, Jingyi Niu, Jinyao Ren, Lei Gao, Yuxin Dong，Ming Yang, Huan Wang