Michal Johnson Joy, Reichelt Michael, Vadassery Jyothilakshmi, Gershenzon Jonathan, Oelmüller Ralf
Institute of General Botany and Plant Physiology, Friedrich-Schiller-University Jena, Dornburger Str, 159, 07743 Jena, Germany.
BMC Plant Biol. 2014 Jun 11;14:162. doi: 10.1186/1471-2229-14-162.
Ca2+, a versatile intracellular second messenger in various signaling pathways, initiates many responses involved in growth, defense and tolerance to biotic and abiotic stress. Endogenous and exogenous signals induce cytoplasmic Ca2+ ([Ca2+]cyt) elevation, which are responsible for the appropriate downstream responses.
Here we report on an ethyl-methane sulfonate-mediated Arabidopsis mutant that fails to induce [Ca2+]cyt elevation in response to exudate preparations from the pathogenic mibrobes Alternaria brassicae, Rhizoctonia solani, Phytophthora parasitica var. nicotianae and Agrobacterium tumefaciens. The cytoplasmic Ca2+elevation mutant1 (cycam1) is susceptible to infections by A. brassicae, its toxin preparation and sensitive to abiotic stress such as drought and salt. It accumulates high levels of reactive oxygen species and contains elevated salicylic acid, abscisic acid and bioactive jasmonic acid iso-leucine levels. Reactive oxygen species- and phytohormone-related genes are higher in A. brassicae-treated wild-type and mutant seedlings. Depending on the analysed response, the elevated levels of defense-related compounds are either caused by the cycam mutation and are promoted by the pathogen, or they are mainly due to the pathogen infection or application of pathogen-associated molecular patterns. Furthermore, cycam1 shows altered responses to abscisic acid treatments: the hormone inhibits germination and growth of the mutant.
We isolated an Arabidopsis mutant which fails to induce [Ca2+]cyt elevation in response to exudate preparations from various microbes. The higher susceptibility of the mutant to pathogen infections correlates with the higher accumulation of defense-related compounds, such as phytohormones, reactive oxygen-species, defense-related mRNA levels and secondary metabolites. Therefore, CYCAM1 couples [Ca2+]cyt elevation to biotic, abiotic and oxidative stress responses.
钙离子（Ca2+）作为多种信号通路中一种多功能的细胞内第二信使，引发许多参与生长、防御以及对生物和非生物胁迫耐受性的反应。内源性和外源性信号诱导细胞质Ca2+（[Ca2+]cyt）升高，这负责适当的下游反应。
在此我们报道了一个由甲基磺酸乙酯介导的拟南芥突变体，该突变体在响应来自致病微生物链格孢、立枯丝核菌、寄生疫霉变种烟草疫霉和根癌农杆菌的分泌物制剂时，无法诱导[Ca2+]cyt升高。细胞质Ca2+升高突变体1（cycam1）对链格孢的感染、其毒素制剂敏感，并且对干旱和盐等非生物胁迫敏感。它积累高水平的活性氧，并且水杨酸、脱落酸和生物活性茉莉酸异亮氨酸水平升高。在链格孢处理的野生型和突变体幼苗中，活性氧和植物激素相关基因表达更高。根据所分析的反应，防御相关化合物水平的升高要么是由cycam突变引起并由病原体促进，要么主要是由于病原体感染或病原体相关分子模式的应用。此外，cycam1对脱落酸处理表现出改变的反应：该激素抑制突变体的萌发和生长。
我们分离出一个拟南芥突变体，其在响应来自各种微生物的分泌物制剂时无法诱导[Ca2+]cyt升高。该突变体对病原体感染的更高易感性与防御相关化合物的更高积累相关，如植物激素、活性氧、防御相关mRNA水平和次生代谢产物。因此，CYCAM1将[Ca2+]cyt升高与生物、非生物和氧化应激反应联系起来。
