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Shohei Katsuta Goro Masuda Hyeokjin Bak Akihisa Shinozawa Yoshiaki Kamiyama Taishi Umezawa Daisuke Takezawa Izumi Yotsui Teruaki Taji Yoichi Sakata 《The Plant journal : for cell and molecular biology》2020,103(2):634-644
Given their sessile nature, land plants must use various mechanisms to manage dehydration under water‐deficit conditions. Osmostress‐induced activation of the SNF1‐related protein kinase 2 (SnRK2) family elicits physiological responses such as stomatal closure to protect plants during drought conditions. With the plant hormone ABA receptors [PYR (pyrabactin resistance)/PYL (pyrabactin resistance‐like)/RCAR (regulatory component of ABA receptors) proteins] and group A protein phosphatases, subclass III SnRK2 also constitutes a core signaling module for ABA, and osmostress triggers ABA accumulation. How SnRK2 is activated through ABA has been clarified, although its activation through osmostress remains unclear. Here, we show that Arabidopsis ABA and abiotic stress‐responsive Raf‐like kinases (AtARKs) of the B3 clade of the mitogen‐activated kinase kinase kinase (MAPKKK) family are crucial in SnRK2‐mediated osmostress responses. Disruption of AtARKs in Arabidopsis results in increased water loss from detached leaves because of impaired stomatal closure in response to osmostress. Our findings obtained in vitro and in planta have shown that AtARKs interact physically with SRK2E, a core factor for stomatal closure in response to drought. Furthermore, we show that AtARK phosphorylates S171 and S175 in the activation loop of SRK2E in vitro and that Atark mutants have defects in osmostress‐induced subclass III SnRK2 activity. Our findings identify a specific type of B3‐MAPKKKs as upstream kinases of subclass III SnRK2 in Arabidopsis. Taken together with earlier reports that ARK is an upstream kinase of SnRK2 in moss, an existing member of a basal land plant lineage, we propose that ARK/SnRK2 module is evolutionarily conserved across 400 million years of land plant evolution for conferring protection against drought. 相似文献
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Alfredo Kono Martin H. Spalding 《The Plant journal : for cell and molecular biology》2020,102(6):1127-1141
In response to high CO2 environmental variability, green algae, such as Chlamydomonas reinhardtii, have evolved multiple physiological states dictated by external CO2 concentration. Genetic and physiological studies demonstrated that at least three CO2 physiological states, a high CO2 (0.5–5% CO2), a low CO2 (0.03–0.4% CO2) and a very low CO2 (< 0.02% CO2) state, exist in Chlamydomonas. To acclimate in the low and very low CO2 states, Chlamydomonas induces a sophisticated strategy known as a CO2‐concentrating mechanism (CCM) that enables proliferation and survival in these unfavorable CO2 environments. Active uptake of Ci from the environment is a fundamental aspect in the Chlamydomonas CCM, and consists of CO2 and HCO3– uptake systems that play distinct roles in low and very low CO2 acclimation states. LCI1, a putative plasma membrane Ci transporter, has been linked through conditional overexpression to active Ci uptake. However, both the role of LCI1 in various CO2 acclimation states and the species of Ci, HCO3– or CO2, that LCI1 transports remain obscure. Here we report the impact of an LCI1 loss‐of‐function mutant on growth and photosynthesis in different genetic backgrounds at multiple pH values. These studies show that LCI1 appears to be associated with active CO2 uptake in low CO2, especially above air‐level CO2, and that any LCI1 role in very low CO2 is minimal. 相似文献
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