XYLOGLUCAN ENDOTRANSGLYCOSYLASE ACTIVITY IN CARROT CELL-SUSPENSIONS DURING CELL ELONGATION AND SOMATIC EMBRYOGENESIS
XYLOGLUCAN ENDOTRANSGLYCOSYLASE ACTIVITY IN CARROT CELL-SUSPENSIONS DURING CELL ELONGATION AND SOMATIC EMBRYOGENESIS
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DOI：
10.1104/pp.103.3.987
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发表时间：
1993-11-01
期刊：
影响因子：
7.4
通讯作者：
FRY, SC
中科院分区：
文献类型：
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作者：
HETHERINGTON, PR;FRY, SC
已经提出木葡聚糖内糖基转移酶（XET）通过壁松弛促进细胞伸长。为了进一步探讨这种关系，我们测定了胡萝卜（Daucus carota L.）表现出不同细胞伸长速率的细胞。在一个细胞系中，通过稀释到不含二氯苯氧乙酸（2，4-D）的培养基中诱导伸长。在此延伸过程中，93%的XET活性被发现在培养基中，相比之下，在nonelongating控制，68%被发现在细胞提取物中，即使这些提取物的比活性低于在延长细胞。到目前为止，每个细胞的XET分泌率最高的是在伸长细胞中。通过稀释到不含2，4-D的培养基中诱导第二细胞系经历体细胞胚胎发生。在第一个6天，许多球形胚状体组成的小，isodiametric细胞在细胞伸长的情况下形成，细胞外XET活性几乎检测不到，细胞内比活性显着下降。6 d后，心形、鱼雷形和子叶形胚状体开始出现（即细胞伸长恢复），细胞内XET比活性迅速上升，超过80%的XET活性在培养基中积累。因此，非扩增细胞悬浮液（无论是否快速分裂）产生和分泌的XET活性低于扩增细胞。我们建议，XET分子有一个短暂的壁松动的作用，而它通过承重层的墙壁上的方式从原生质体进入培养基。
Xyloglucan endotransglycosylase (XET) has been proposed to contribute to cell elongation through wall loosening. To explore this relationship further, we assayed this enzyme activity in suspensions of carrot (Daucus carota L.) cells exhibiting various rates of cell elongation. In one cell line, elongation was induced by dilution into dichlorophenoxyacetic acid (2,4-D)-free medium. During this elongation, 93% of the XET activity was found in the culture medium; in nonelongating controls, by contrast, 68% was found in the cell extracts even though the specific activity of these extracts was lower than in the elongating cells. By far the highest rates of XET secretion per cell were in the elongating cells. A second cell line was induced to undergo somatic embryogenesis by dilution into 2,4-D-free medium. During the first 6 d, numerous globular embryoids composed of small, isodiametric cells were formed in the absence of cell elongation; extracellular XET activity was almost undetectable, and intracellular specific activity markedly declined. After 6 d, heart, torpedo, and cotyledonary embryoids began to appear (i.e. cell elongation resumed); the intracellular specific activity of XET rose rapidly and >80% of the XET activity accumulated in the medium. Thus, nonexpanding cell suspensions (whether or not they were rapidly dividing) produced and secreted less XET activity than did expanding cells. We propose that a XET molecule has an ephemeral wall-loosening role while it passes through the load-bearing layer of the wall on its way from the protoplast into the culture medium.