Changes in the apoplastic pH are involved in regulation of xyloglucan breakdown of azuki bean epicotyls under hypergravity conditions.
Changes in the apoplastic pH are involved in regulation of xyloglucan breakdown of azuki bean epicotyls under hypergravity conditions.
复制标题
质外体 pH 值的变化参与超重力条件下小豆上胚轴木葡聚糖分解的调节。
DOI：
10.1093/pcp/41.4.509
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发表时间：
2000
影响因子：
4.9
通讯作者：
S. Kamisaka
中科院分区：
文献类型：
--
作者：
K. Soga;K. Wakabayashi;T. Hoson;S. Kamisaka
超重力通过木糖葡聚糖分子质量的增加，降低细胞壁的机械伸长性，从而抑制了azuki bean （Vigna angularis Ohwi et Ohashi）上胚轴的伸长生长[Soga et al. (1999) Plant cell physil . 40: 581]。在这里，我们报道了在超重力（300 x g）处理下，上胚轴的外胞液pH值从5.8增加到6.6。从1 × g对照上胚轴细胞壁提取的木葡聚糖降解酶在pH 6.6和5.8的缓冲液中进行测定，pH 6.6的活性几乎是pH 5.8的一半。另外，将1 x g对照上胚的酶活性细胞壁制剂在pH 5.8和6.6的缓冲液中自溶，然后从自溶的细胞壁中提取木葡聚糖，在pH 5.8下培养的木葡聚糖在自溶过程中分子质量下降，而在pH 6.6下没有变化。因此，在超重处理的上胚轴中观察到的pH值（6.6）下，木葡聚糖不能通过自溶解聚。这些结果表明，在红豆上胚轴中，超重通过增加胞外液的pH值来降低木葡聚糖降解酶的活性，这可能参与了木葡聚糖分子质量增加的过程，导致细胞壁伸展性降低。
Hypergravity inhibited elongation growth of azuki bean (Vigna angularis Ohwi et Ohashi) epicotyls by decreasing the mechanical extensibility of cell walls via the increase in the molecular mass of xyloglucans [Soga et al. (1999) Plant Cell Physiol. 40: 581]. Here, we report that the pH value of the apoplastic fluid in epicotyls increased from 5.8 to 6.6 by hypergravity (300 x g) treatment. When the xyloglucan-degrading enzymes extracted from cell walls of the 1 x g control epicotyls were assayed in buffer at pH 6.6 and 5.8, the activity at pH 6.6 was almost half of that at pH 5.8. In addition, when enzymically active cell wall preparations obtained from 1 x g control epicotyls were autolyzed in buffer at pH 5.8 and 6.6 and then xyloglucans were extracted from the autolyzed cell walls, the molecular mass of xyloglucans incubated at pH 5.8 decreased during the autolysis, while that at pH 6.6 did not change. Thus, the xyloglucans were not depolymerized by autolysis at the pH value (6.6) observed in the hypergravity-treated epicotyls. These findings suggest that in azuki bean epicotyls, hypergravity decreases the activities of xyloglucan-degrading enzymes by increasing the pH in the apoplastic fluid, which may be involved in the processes of the increase in the molecular mass of xyloglucans, leading to the decrease in the cell wall extensibility.