Mizuno Hidetoshi, Kobayashi Akie, Fujii Nobuharu, Yamashita Masamichi, Takahashi Hideyuki
Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 Japan.
Plant Cell Physiol. 2002 Jul;43(7):793-801. doi: 10.1093/pcp/pcf093.
Primary roots of cucumber seedlings showed positive hydrotropism when exposed to a moisture gradient and rotated on a two-axis clinostat. To examine the role of auxin in the differential growth of the hydrotropically responding roots, we first examined the expression of auxin-inducible genes, CS-AUX/IAAs, in cucumber roots. After auxin starvation, mRNA levels of CS-IAA1 and CS-IAA3 decreased in the roots. Applying auxin to the auxin-starved roots resulted in accumulation of CS-IAA1 and CS-IAA3 mRNA. The level of expression of these genes increased when the auxin concentration was increased. CS-IAA1 mRNA accumulated in response to 10(-8) M auxin, and the level increased further, depending on the dose. Auxin starvation did not result in a decrease in the level of CS-IAA2 mRNA; however, adding exogenous auxin at concentrations higher than 10(-7) M increased its accumulation. In the primary roots responding hydrotropically or gravitropically, CS-IAA1 expression was greater on the concave side of the curving roots than on the convex side. The difference could be detected 30 min following stimulation by gravity or a moisture gradient, and that difference increased with time. These results support the idea that asymmetry of localization of auxin is associated with differential growth in hydrotropically responding roots.
黄瓜幼苗的初生根在暴露于湿度梯度并在双轴回转器上旋转时表现出正向水性。为了研究生长素在向水性响应根的差异生长中的作用，我们首先检测了黄瓜根中生长素诱导基因CS-AUX/IAAs的表达。生长素饥饿后，根中CS-IAA1和CS-IAA3的mRNA水平下降。向生长素饥饿的根中施加生长素导致CS-IAA1和CS-IAA3 mRNA的积累。当生长素浓度增加时，这些基因的表达水平升高。CS-IAA1 mRNA在10(-8)M生长素作用下积累，且水平随剂量进一步升高。生长素饥饿并未导致CS-IAA2 mRNA水平下降；然而，添加高于10(-7)M浓度的外源生长素会增加其积累。在向水性或向重力性响应的初生根中，CS-IAA1在弯曲根的凹侧的表达高于凸侧。在重力或湿度梯度刺激后30分钟即可检测到这种差异，且这种差异随时间增加。这些结果支持了生长素定位不对称与向水性响应根的差异生长相关的观点。
