Adaptive strategies of plants to drought and high-temperature conditions and their control for plant cultivation in arid area

为了获得植物适应策略的基础知识，并开发可用于干旱地区植物栽培的新方法和新植物，我们研究了小麦幼苗耐深播、根系亲水性和高温诱导雄性不育的机理。耐深播小麦品种对赤霉素(GA)更为敏感，在黑暗条件下经GA处理的第一节间伸长超过40 cm。因此，即使在40厘米深的土壤中，幼苗也能成功出苗。小麦的这种GA反应是通过同时从培养液中吸收钾以实现细胞渗透调节和螺旋生长以降低土壤中的机械阻抗来实现的。我们建立了一个研究拟南芥根的亲水性的实验系统，揭示了脱落酸、生长素和挥发反应与亲水性的关系。此外，我们还发现，水分梯度或水分胁迫导致拟南芥根小柱细胞中淀粉锚--淀粉质的立即降解，从而降低了根对重力的响应，从而使它们在不受向重力性干扰的情况下表现出亲水性。此外，我们还分离到了拟南芥独特的亲水性突变体，这使得我们能够剖析苗期根系亲水性的分子机制。我们发现，花器官发生期间的高温诱导大麦雄性不育。对于雄性不育，高温抑制了组蛋白H3、H4和富含甘氨酸的RNA结合蛋白基因的表达，这些基因的表达在花药发育之前被显著诱导。此外，还表明大麦花药的早期发育和分化对高温胁迫非常敏感，这是由于转录受到抑制。

To obtain fundamental knowledge on the adaptive strategies of plants and to develop new methods and plants that could be used for plant cultivation in arid area, we studied the mechanisms for deep-sowing tolerance of seedlings, root hydrotropism, and high-temperature-induced male sterility.Wheat seedlings emerge from the soil by elongating their first internodes. A variety of wheat tolerant to deep-sowing conditions was more sensitive to gibberellin (GA); the first internodes treated with GA elongated longer than 40 cm in the dark. Accordingly, the seedlings successfully emerged even from 40-cm depth in the soil. This GA response of the wheat was achieved by accompanying simultaneous uptake of potassium from the culture media for cellular osmoregulaiion and spiral growth for reducing mechanical impedance in the soil.We established an experimental system for the study of hydrotropism in Arabidopsis roots and revealed the involvement of abscisic acid, auxin and waving response with hydrotropism. In addition, we found that moisture gradient or water stress caused immediate degradation of the starch anchors, amyloplasts, in columella cells of Arabidopsis roots, which reduced the responsiveness of roots to gravity and thus allowed them to exhibit hydrotropism without interference by gravitropism. Also, we isolated unique hydrotropic mutants of Arabidopsis, which enabled us to dissect molecular mechanism for hydrotropism in seedling roots.We found that high temperature during floral organogenesis induced male sterility in barley. In relation to the male sterility, high temperature inhibited the expression of histone H3,H4 and glycine-rich RNA binding protein genes whose expressions are dramatically induced just before anther development. Furthermore, it was suggested that the early development and differentiation of barley anthers are hypersensitive to high temperature stress due to the inhibited transcriptions.