Campos F, Perez-Castiñeira J R, Villalba J M, Culiañez-Marciá F A, Sánchez F, Serrano R
Instituto de Biologia Molecular y Celular de Plantas, Universidad Politécnica de Valencia-C.S.I.C., Spain.
Plant Mol Biol. 1996 Dec;32(6):1043-53. doi: 10.1007/BF00041388.
Legume nodules have specialized transport functions for the exchange of carbon and nitrogen compounds between bacteroids and root cells. Plasma membrane-type (vanadate-sensitive) H+-ATPase energizes secondary active transporters in plant cells and it could drive exchanges across peribacteroidal and plasmatic membranes. A nodule cDNA corresponding to a major isoform of Phaseolus vulgaris H+-ATPase (designated BHA1) has been cloned. BHA1 is a functional proton pump because after removal of its inhibitory domain and can complement a yeast mutant unable to synthesize a H+-ATPase. BHA1 is not nodule-specific, since it is also expressed in roots of uninfected plants. It belongs to the subfamily of plasma membrane H+-ATPases defined by the Arabidopsis AHA1, AHA2 and AHA3 genes and the tobacco PMA4 and corn MHA2 genes. In situ hybridization in nodule sections indicates high expression of BHA1 limited to uninfected cells. These results were confirmed by immunocytochemistry. The relatively low expression of plasma membrane-type H+-ATPase in Rhizobium-infected cells put a note of caution on the origin of the vanadate-sensitive ATPase described in preparations of peribacteroidal membranes. Also, our results indicate that active transport in symbiotic nodules is most intense at the plasma membrane of uninfected cells and support a specialized role of uninfected tissue for nitrogen transport.
豆科植物根瘤具有专门的运输功能，用于类菌体与根细胞之间碳和氮化合物的交换。质膜型（钒酸盐敏感型）H⁺-ATP酶为植物细胞中的次级主动转运蛋白提供能量，它可以驱动类菌体周膜和质膜上的交换。一个与菜豆H⁺-ATP酶的主要同工型（命名为BHA1）对应的根瘤cDNA已被克隆。BHA1是一种功能性质子泵，因为去除其抑制结构域后，它可以补充一个无法合成H⁺-ATP酶的酵母突变体。BHA1并非根瘤特异性的，因为它在未感染植物的根中也有表达。它属于由拟南芥AHA1、AHA2和AHA3基因以及烟草PMA4和玉米MHA2基因所定义的质膜H⁺-ATP酶亚家族。根瘤切片的原位杂交表明BHA1的高表达仅限于未感染细胞。这些结果通过免疫细胞化学得到了证实。根瘤菌感染细胞中质膜型H⁺-ATP酶的相对低表达，对于类菌体周膜制剂中所描述的钒酸盐敏感型ATP酶的来源提出了警示。此外，我们的结果表明共生根瘤中的主动运输在未感染细胞的质膜处最为强烈，并支持未感染组织在氮运输中的特殊作用。
