Department of Plant Sciences, University of California, Davis, CA, USA.
Plant Biotechnol J. 2011 Sep;9(7):747-58. doi: 10.1111/j.1467-7652.2010.00584.x. Epub 2011 Feb 1.
Drought is the major environmental factor limiting crop productivity worldwide. We hypothesized that it is possible to enhance drought tolerance by delaying stress-induced senescence through the stress-induced synthesis of cytokinins in crop-plants. We generated transgenic rice (Oryza sativa) plants expressing an isopentenyltransferase (IPT) gene driven by P(SARK) , a stress- and maturation-induced promoter. Plants were tested for drought tolerance at two yield-sensitive developmental stages: pre- and post-anthesis. Under both treatments, the transgenic rice plants exhibited delayed response to stress with significantly higher grain yield (GY) when compared to wild-type plants. Gene expression analysis revealed a significant shift in expression of hormone-associated genes in the transgenic plants. During water-stress (WS), P(SARK)::IPT plants displayed increased expression of brassinosteroid-related genes and repression of jasmonate-related genes. Changes in hormone homeostasis were associated with resource(s) mobilization during stress. The transgenic plants displayed differential expression of genes encoding enzymes associated with hormone synthesis and hormone-regulated pathways. These changes and associated hormonal crosstalk resulted in the modification of source/sink relationships and a stronger sink capacity of the P(SARK)::IPT plants during WS. As a result, the transgenic plants had higher GY with improved quality (nutrients and starch content).
干旱是全球范围内限制作物生产力的主要环境因素。我们假设，通过在作物中应激诱导合成细胞分裂素来延迟应激诱导的衰老，从而有可能提高耐旱性。我们生成了表达异戊烯基转移酶（IPT）基因的转基因水稻（Oryza sativa）植株，该基因由 P（SARK）启动子驱动，该启动子受应激和成熟诱导。在两个对产量敏感的发育阶段对植物进行了耐旱性测试：开花前和开花后。在这两种处理下，与野生型植物相比，转基因水稻植株对胁迫的反应明显延迟，且粒产量（GY）显著提高。基因表达分析显示，在转基因植物中，与激素相关的基因表达发生了显著变化。在水分胁迫（WS）期间，P（SARK）：：IPT 植物表现出与油菜素内酯相关基因的表达增加和与茉莉酸相关基因的表达抑制。激素稳态的变化与胁迫期间资源动员有关。转基因植物表现出与激素合成和激素调节途径相关的酶编码基因的差异表达。这些变化和相关的激素串扰导致了 P（SARK）：：IPT 植物在 WS 期间源/库关系的改变和更强的库容量。结果，转基因植物的产量更高，品质（营养物质和淀粉含量）也得到了改善。
