Dehio C, de Bruijn F J
Max-Planck-Institut für Züchtungsforschung, Abteilung Genetische Grundlagen der Pflanzenzüchtung, Köln, Germany.
Plant J. 1992 Jan;2(1):117-28. doi: 10.1046/j.1365-313x.1992.t01-51-00999.x.
The structure and expression of the early nodulin gene Enod2 from the stem-nodulated tropical legume Sesbania rostrata (SrEnod2) was examined. Genomic clones carrying the single SrEnod2locus were isolated and the DNA sequence of the gene was determined. The SrEnod2 gene was found to lack introns and to encode a protein consisting primarily of a 55-fold repeat of short proline-rich oligopeptides. A putative signal sequence, which may be responsible for targeting of the Enod2 protein to the cell wall, was found to precede this repeat. The temporal expression of the SrEnod2 gene was found to be different in S. rostrata stem versus root nodules induced by Azorhizobium caulinodans ORS571. SrEnod2 gene expression was shown to be induced specifically and rapidly by physiologically significant concentrations of exogenously supplied cytokinins. The SrEnod2 gene was also found to be highly expressed in S. rostrata crown gall tumors induced by wild-type Agrobacterium tumefaciens strains, but not in tumors induced by an A. tumefaciens strain carrying a mutation in the cytokinin biosynthesis gene 4. Implications of these observations with regard to cytokinin-induced plant gene expression and a possible role for cytokinin as a symbiotic signal are discussed.
对热带茎瘤豆科植物喙荚田菁（SrEnod2）中早期结瘤素基因Enod2的结构和表达进行了研究。分离出携带单个SrEnod2基因座的基因组克隆，并测定了该基因的DNA序列。发现SrEnod2基因不含内含子，编码一种主要由富含脯氨酸的短寡肽55倍重复序列组成的蛋白质。在该重复序列之前发现了一个推定的信号序列，它可能负责将Enod2蛋白靶向细胞壁。结果发现，SrEnod2基因在茎瘤和由茎瘤固氮根瘤菌ORS571诱导的根瘤中的表达时间不同。生理浓度的外源细胞分裂素能特异性快速诱导SrEnod2基因表达。还发现SrEnod2基因在野生型根癌农杆菌菌株诱导的喙荚田菁冠瘿瘤中高表达，但在携带细胞分裂素生物合成基因4突变的根癌农杆菌菌株诱导的肿瘤中不表达。讨论了这些观察结果对细胞分裂素诱导植物基因表达的意义以及细胞分裂素作为共生信号的可能作用。
