Cervantes-Chávez José Antonio, Ali Shawkat, Bakkeren Guus
Agriculture and AgriFood Canada, Pacific Agri-Food Research Centre, Summerland, BC, V0H 1Z0, Canada.
Mol Plant Microbe Interact. 2011 Feb;24(2):219-32. doi: 10.1094/MPMI-09-10-0202.
In eukaryotes, several biological processes are regulated through calcium signaling. Calcineurin is a calcium-calmodulin-regulated serine/threonine phosphatase consisting of catalytic subunit A and regulatory subunit B. Phosphatase activity resides in the catalytic subunit, which activates by dephosphorylation downstream components such as transcription factor Crz1. The importance of this pathway to respond to environmental stress has been explored in several fungal pathogens. The basidiomycete Ustilago hordei causes covered smut of barley. We addressed the role of the Ca(2+)-calcineurin activated pathway by deleting UhCna1 and UhCnb1. These genes were not essential in U. hordei but the corresponding mutants displayed a variety of phenotypes when applying environmental stress such as sensitivity to pH, temperature, H₂O₂, mono- and divalent cations; and to genotoxic, acid, or oxidative stresses. Cell-wall integrity was compromised and mutants displayed altered cell morphologies. Mating was delayed but not abolished, and combined sensitivities likely explained a severely reduced virulence toward barley plants. Expression analyses revealed that response to salt stress involved the induction of membrane ATPase genes UhEna1 and UhEna2, which were regulated through the calcineurin pathway. Upregulation of UhFKS1, a 1,3-β-d-glucan synthase gene, correlated with the increased amount of 1,3-β-d-glucan in the calcineurin mutants grown under salt stress.
在真核生物中，多种生物学过程通过钙信号传导进行调控。钙调神经磷酸酶是一种由催化亚基A和调节亚基B组成的钙-钙调蛋白调节的丝氨酸/苏氨酸磷酸酶。磷酸酶活性存在于催化亚基中，该亚基通过使下游成分（如转录因子Crz1）去磷酸化而激活。这条途径在应对环境胁迫中的重要性已在几种真菌病原体中得到研究。担子菌纲的大麦坚黑粉菌会引起大麦的散黑穗病。我们通过缺失UhCna1和UhCnb1来研究Ca(2+)-钙调神经磷酸酶激活途径的作用。这些基因在大麦坚黑粉菌中并非必需，但相应的突变体在施加环境胁迫时表现出多种表型，如对pH、温度、H₂O₂、单价和二价阳离子敏感；以及对基因毒性、酸性或氧化胁迫敏感。细胞壁完整性受到损害，突变体表现出细胞形态改变。交配延迟但未被消除，综合敏感性可能解释了对大麦植株的毒力严重降低。表达分析表明，对盐胁迫的反应涉及膜ATP酶基因UhEna1和UhEna2的诱导，这些基因通过钙调神经磷酸酶途径进行调控。1,3-β-D-葡聚糖合酶基因UhFKS1的上调与盐胁迫下生长的钙调神经磷酸酶突变体中1,3-β-D-葡聚糖含量的增加相关。
