Vadassery Jyothilakshmi, Tripathi Swati, Prasad Ram, Varma Ajit, Oelmüller Ralf
Friedrich-Schiller-Universität Jena, Institut für Allgemeine Botanik und Pflanzenphysiologie, Dornburger Str. 159, 07743 Jena, Germany.
Amity Institute of Herbal and Microbial Studies, Sector 125, Noida 201303, UP, India.
J Plant Physiol. 2009 Aug 15;166(12):1263-1274. doi: 10.1016/j.jplph.2008.12.016. Epub 2009 Apr 21.
Ascorbate is a major antioxidant and radical scavenger in plants. Monodehydroascorbate reductase (MDAR) and dehydroascorbate reductase (DHAR) are two enzymes of the ascorbate-glutathione cycle that maintain ascorbate in its reduced state. MDAR2 (At3g09940) and DHAR5 (At1g19570) expression was upregulated in the roots and shoots of Arabidopsis seedlings co-cultivated with the root-colonizing endophytic fungus Piriformospora indica, or that were exposed to a cell wall extract or a culture filtrate from the fungus. Growth and seed production were not promoted by Piriformospora indica in mdar2 (SALK_0776335C) and dhar5 (SALK_029966C) T-DNA insertion lines, while colonized wild-type plants were larger and produced more seeds compared to the uncolonized controls. After 3 weeks of drought stress, growth and seed production were reduced in Piriformospora indica-colonized plants compared to the uncolonized control, and the roots of the drought-stressed insertion lines were colonized more heavily by the fungus than were wild-type plants. Upregulation of the message for the antimicrobial PDF1.2 protein in drought-stressed insertion lines indicated that MDAR2 and DHAR5 are crucial for producing sufficient ascorbate to maintain the interaction between Piriformospora indica and Arabidopsis in a mutualistic state.
抗坏血酸盐是植物中的一种主要抗氧化剂和自由基清除剂。单脱氢抗坏血酸还原酶（MDAR）和脱氢抗坏血酸还原酶（DHAR）是抗坏血酸-谷胱甘肽循环中的两种酶，可使抗坏血酸盐维持在还原状态。在与根部定殖内生真菌印度梨形孢共培养的拟南芥幼苗的根和芽中，或者在暴露于该真菌的细胞壁提取物或培养滤液的拟南芥幼苗的根和芽中，MDAR2（At3g09940）和DHAR5（At1g19570）的表达上调。在mdar2（SALK_0776335C）和dhar5（SALK_029966C）T-DNA插入系中，印度梨形孢并未促进生长和种子产量，而与未定殖的对照相比，定殖的野生型植物更大且产生更多种子。干旱胁迫3周后，与未定殖的对照相比，印度梨形孢定殖的植物的生长和种子产量降低，并且干旱胁迫插入系的根比野生型植物被该真菌定殖得更严重。干旱胁迫插入系中抗菌PDF1.2蛋白的信息上调表明，MDAR2和DHAR5对于产生足够的抗坏血酸盐以维持印度梨形孢与拟南芥之间的互利共生状态的相互作用至关重要。
