van de Wiel C, Scheres B, Franssen H, van Lierop M J, van Lammeren A, van Kammen A, Bisseling T
Department of Molecular Biology, Agricultural University, Wageningen, The Netherlands.
EMBO J. 1990 Jan;9(1):1-7. doi: 10.1002/j.1460-2075.1990.tb08073.x.
A pea cDNA clone homologous to the soybean early nodulin clone pGmENOD2 that most probably encodes a cell wall protein was isolated. The derived amino acid sequence of the pea ENOD2 protein shows that it contains the same repeating pentapeptides, ProProHisGluLys and ProProGluTyrGln, as the soybean ENOD2 protein. By in situ hybridization the expression of the ENOD2 gene was shown to occur only in the inner cortex of the indeterminate pea nodule. The transcription of the pea ENOD2 gene starts when the inner cortical cells develop from the nodule meristem. In the determinate soybean nodule the ENOD2 gene is expressed in the inner cortex as well as in cells surrounding the vascular bundle that connects the nodule with the root central cylinder. The term 'nodule inner cortex' is misleading, as there is no direct homology with the root inner cortex. Therefore, we propose to consider this tissue as nodule parenchyma. A possible role of ENOD2 in a major function of the nodule parenchyma, namely creating an oxygen barrier for the central tissue with the Rhizobium containing cells, is discussed.
分离出了一个与大豆早期结瘤素克隆pGmENOD2同源的豌豆cDNA克隆，该克隆很可能编码一种细胞壁蛋白。豌豆ENOD2蛋白的推导氨基酸序列表明，它与大豆ENOD2蛋白含有相同的重复五肽，即ProProHisGluLys和ProProGluTyrGln。通过原位杂交表明，ENOD2基因仅在不定型豌豆根瘤的内皮层中表达。豌豆ENOD2基因的转录始于内皮层细胞从根瘤分生组织发育之时。在定型的大豆根瘤中，ENOD2基因在内皮层以及连接根瘤与根中央柱的维管束周围的细胞中表达。术语“根瘤内皮层”具有误导性，因为它与根的内皮层没有直接的同源性。因此，我们建议将该组织视为根瘤薄壁组织。本文讨论了ENOD2在根瘤薄壁组织的主要功能中的可能作用，即在含根瘤菌的细胞与中央组织之间形成氧气屏障。
