Clement Mathilde, Boncompagni Eric, de Almeida-Engler Janice, Herouart Didier
Unité Mixte de Recherche (UMR) 'Interactions Plantes Microorganimes et Santé Végétale' INRA1064-CNRS 6192-Université de Nice-Sophia Antipolis, Institut Sophia Agrobiotech, 400 Routes des Chappes, 06903 Sophia-Antipolis Cedex, France.
Plant Cell Environ. 2006 Sep;29(9):1841-52. doi: 10.1111/j.1365-3040.2006.01558.x.
Symbiotic N(2) fixation of legume crops is highly sensitive to drought, which results in a dramatic drop of N accumulation and yield. The symbiosis between soybean (Glycine max) and Bradyrhizobium japonicum, because of its extreme sensitivity to drought, was chosen as a model to analyse the response to drought stress at a molecular level. The mRNA differential display technique was performed to isolate cDNA markers differentially expressed in well-watered [100% of N(2) fixation capacity (NFC)] and drought-stressed nodules (40% NFC). One gene noted, G93, appeared strongly down-regulated by drought and fully recovered after rehydration. In situ hybridization showed that G93 transcripts were localized in N(2)-fixing cells of mature nodules, indicating that G93 could be considered as a late nodulin. However, G93 expression was not directly correlated to N(2) fixation but mainly responded to osmotic stress. Other stresses that lead to decrease of N(2) fixation did not affect G93 expression. Sequence analyses showed that G93 presented a strong homology with two soybean expressed sequence tags (ESTs) and with the ZR1 protein of Medicago sativa. Putative roles of this nodulin in adaptation of soybean nodule to osmotic stress are proposed.
豆科作物的共生固氮对干旱高度敏感，这会导致氮积累和产量急剧下降。大豆（Glycine max）与日本慢生根瘤菌之间的共生关系因其对干旱极度敏感，被选作模型来在分子水平分析对干旱胁迫的响应。采用mRNA差异显示技术分离在水分充足[固氮能力（NFC）的100%]和干旱胁迫的根瘤（NFC的40%）中差异表达的cDNA标记。一个名为G93的基因在干旱处理下强烈下调，并在复水后完全恢复。原位杂交表明，G93转录本定位于成熟根瘤的固氮细胞中，这表明G93可被视为一种晚期根瘤蛋白。然而，G93的表达与固氮没有直接关联，主要是对渗透胁迫作出响应。其他导致固氮减少的胁迫并未影响G93的表达。序列分析表明，G93与两个大豆表达序列标签（EST）以及苜蓿的ZR1蛋白具有高度同源性。本文提出了这种根瘤蛋白在大豆根瘤适应渗透胁迫中的假定作用。
