Functions of water channel in the growth and development of horticultural crops.

1、果实水分通道(1)梨幼果液泡膜水分通道(TIP)蛋白水平较高，而葡萄浆果液泡膜水分通道(PIP)和液泡膜水分通道(PIP)蛋白水平在发育过程中基本不变。说明水分通道在水分调节中起作用，而不是果实发育。(2)幼龄梨果实TIP基因表达水平较高，而PIP基因在果实发育过程中几乎保持不变水平。TIP和PIP基因在果实中的表达尤其高于其他器官，表明水分通道在果实中的重要性。(3)利用仅能识别磷酸化PIP2的抗体检测PIP2的磷酸化。2.萝卜水分通道(1)在幼根和下胚轴的中央圆柱体、叶柄的束鞘等发育组织或维管组织中，PIP和PIP的蛋白和基因表达水平较高。这符合生理功能。(2)测定了表达的酵母膜的水分转运。TIP和PIP2输送水分。另一方面，PIPI不运输水分，可能起到水分运输以外的作用。(3)对萝卜幼苗进行渗透胁迫或植物激素处理后，TIP和PIP1的mRNA和蛋白质水平没有变化，而PIP2的mRNA和蛋白质水平发生了变化。结果表明，萝卜的TIP和PIP为管家类型，PIP2为环境诱导型。(4)萝卜下胚轴的表皮细胞和主根的薄壁细胞高水平表达水分通道，其水分运输活性也很高(300-500 mm/s)。

1, Water Channel in Fruit(1)Protein level of tonoplast water channel (TIP) of pear was high in young fruit, on the other hand, that of TIP and plasma membrane water channel (PIP) of grape berry was the almost constant during development. This suggests that water channel a play role in water regulation rather than fruit development.(2)Gene expression of TIP was high in young pear fruit, but that of PIP showed almost constant level during development. Gene expressions of TIP and PIP in fruit was especially higher than those in other organs, suggesting the importance of water channel in fruit.(3)Phosphorylation of PIP2 was determined using the antibody which could recognize only phosphorylated PIP2. PIP2 was de-phospholylared by salt and osmotic stresses and also in the fruit in day time.2, Water Channel in Radish(1)Protein and gene expressions of TIP and PIP were high in developing tissue or vascular tissue, such as central cylinder in young root and hypocotyl, and bundle sheath in petiole. This meets physiological function.(2)Water transport of the membrane from yeast expressed each TIP or PIP was measured. TIP and PIP2 transported water. On the other hand, PIPI did not transport water and it might play a role other than water transport.(3)By the treatment of osmotic stress or plant hormone to radish seedling, mRNA and protein levels of TIP and PIPL did not change, but those of PIP2 did. These results show that TIP and PIP are housekeeping type and PIP2 is environmentally inducible one.(4)The epidermis cells of hypocotyl and the parenchyma cells of taproot of radish were expressed water channels at high levels and their water transport activities were also high (300-500 mm/sec).