Golgi‐localized cation/proton exchangers regulate ionic homeostasis and skotomorphogenesis in Arabidopsis. (25th November 2018) - Wang, Yuan
Abstract: Multiple transporters and channels mediate cation transport across the plasma membrane and tonoplast to regulate ionic homeostasis in plant cells. However, much less is known about the molecular function of transporters that facilitate cation transport in other organelles such as Golgi. We report here that Arabidopsis KEA4, KEA5, and KEA6, members of cation/proton antiporters‐2 (CPA2) superfamily were colocalized with the known Golgi marker, SYP32‐mCherry. Although single kea4, 5, 6 mutants showed similar phenotype as the wild type under various conditions, kea4/5/6 triple mutants showed hypersensitivity to low pH, high K +, and high Na + and displayed growth defects in darkness, suggesting that these three KEA‐type transporters function redundantly in controlling etiolated seedling growth and ion homeostasis. Detailed analysis indicated that the kea4/5/6 triple mutant exhibited cell wall biosynthesis defect during the rapid etiolated seedling growth and under high K + /Na + condition. The cell wall‐derived pectin homogalacturonan (GalA)3 partially suppressed the growth defects and ionic toxicity in the kea4/5/6 triple mutants when grown in the dark but not in the light conditions. Together, these data support the hypothesis that the Golgi‐localized KEAs play key roles in the maintenance of ionic and pH homeostasis, thereby facilitating Golgi function in cell wall biosynthesis during rapid etiolated seedling growth and in coping with high K + /Na + stress. Abstract : Plastidial K + transporters KEA1, KEA2, and KEA3 have been reported to play important roles in chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis . However, much less is known about the molecular identity and function of KEA4, KEA5, and KEA6. In our report, we demonstrate that the Golgi‐localized KEA4, KEA5, and KEA6 play key roles in the maintenance of ionic and pH homeostasis, thereby facilitating Golgi function in cell wall biosynthesis during rapid cell growth of etiolated seedlings and in coping with high K + /Na + stress. This study represents the first functional analysis of these three transporters in any plant species.