【目的】探讨气培条件下，IAA 极性运输对水稻根毛形成及水通道蛋白基因表达的影响。【方法】以超表达OsPIN1a的转基因水稻和野生型水稻为研究材料，当种子根长为0.5—1.0 cm时，分别用不同浓度IAA、IAA和生长素极性运输输出载体抑制剂、IAA 和生长素输入载体抑制剂复合处理的琼脂块贴在根尖一侧，黑暗条件下培养12 h后观察根毛生长情况，测定根毛的密度、长度及根毛形成后根尖部分相对含水量，并用激光共聚焦显微镜观察根尖及根毛内的OsPIN1a-GFP亚细胞定位，再通过半定量RT-PCR检测根毛形成前后水通道蛋白基因表达。【结果】（1）在0—5.0 mg·L-1 IAA浓度范围内，随IAA浓度增加，根毛长度和密度也增加，当浓度超过5.0 mg·L-1时，根毛长度和密度不再增加，根的生长受到显著抑制，2.5 mg·L-1 IAA诱导效果最好；（2）只有根尖分生区IAA处理后，才能诱导新的根毛区形成根毛，而其他区域处理后无法诱导根毛形成；（3）根毛形成不受低浓度的生长素极性运输输出载体抑制剂TIBA、NPA和IAA复合处理的影响，高浓度TIBA、NPA和IAA复合处理则显著抑制根毛形成及根的生长；（4）低浓度生长素极性运输输入载体抑制剂CHPAA和IAA复合处理能显著抑制根毛形成和根的生长；（5）IAA 不但能诱导根毛形成，也能诱导多种水通道蛋白基因表达，提高根尖相对含水量；（6）根尖及根毛内的OsPIN1a基因的表达和OsPIN1a-GFP含量均受IAA诱导，并在根毛细胞内大量表达。【结论】在气培条件下，根毛形成需要IAA诱导，而IAA诱导根毛形成过程需要生长素极性运输输入和输出载体蛋白的参与，其中输入过程对根毛的形成影响最大。IAA 极性运输输入或输出载体蛋白特异性抑制剂处理显著降低根毛形成和根的生长，因此OsPIN1a在根毛形成中起着重要作用，同时根毛水通道蛋白基因表达量增加，提高了根尖相对含水量，减缓了气培条件下水稻根尖的水分胁迫。%Objective]To explore the effect of auxin (IAA) and its polar auxin transport carriers on the formation of rice root hair and genetic expression of aquaporins.[Method]The varieties of wild-typeJaponicarice Zhonghua11 and its over-expressed OsPIN1a transgenic rice primary root were used in this paper. A small agar block which contains different concentrations of IAA and combination of IAA and inhibitors of polar auxin transport efflux carrier TIBA (2, 3, 5-Triiodobenzoic acid), NPA (N-1-naphthylphthalamic acid) or polar auxin transport influx carrier CHPAA (3-Chloro-4-hydroxyphenylacetic acid) was affixed to the lateral side of rice root tip when the primary root reached 0.5—1.0 cm in length in a aeroponic and dark culture. After a 12h treatment, the root hair length, root growth rate, root hair density and relative water content in rice roots were detected. The photos were taken by confocal laser scanning microscope (Zeiss Axiophot microscope with a Qimaging Retiga 1300 12-bit monochrome CCD camera with Open Lab v3.0.9) to observe subcellular localization of OsPIN1a-GFPin the tip and hair of the rice root. In addition, semi-quantitative RT-PCR was applied to detecting theOsPIN1a and aquaporins genes expression before and after the formation of the rice root hair.[Result]The results showed that the length and density of the root hair enhanced correspondingly with an increase in IAA concentration range from 0 to 5.0 mg·L-1, and 2.5 mg·L-1 IAA had an optimal effect on inducing the formation of root hair. However, as IAA exceeds 5.0 mg·L-1, the increase in root hair was insignificant and thus the primary root growth was severely inhibited. The new root hair only appeared when agar was attached to the meristematic zone of root tip but not formed in the ripe areas of the primary root. Combined treatment with IAA and lower concentration of TIBA or NPA did not affect formation of root hairs. In contrast, higher concentration of TIBA or NPA significantly inhibited its formation and elongation. However, much lower concentrations of CHPAA can significantly inhibit the formation and elongation of the root hair. In addition, IAA treatment increased genes expression of aquaporins as well as the formation of the root hair, thus improving the relative content of water in root tips. IAA treatment markedly improved the expression ofOsPIN1a and the content of OsPIN1a-GFP in root tips and root hair.[Conclusion]It was suggested that the formation of rice root hair was induced by IAA and associated with the involvement of IAA efflux and influx transporters and influx process had the most significant effect. OsPIN1a played a key role in the formation and elongation of the root hair. IAA can promote genes expression of aquaporins and increase relative water content, thus alleviating water stress in rice roots in the aeroponic culture.
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