Targeting Hormone-Related Pathways to Improve Grain Yield in Rice: A Chemical Approach

Sink/source relationships, regulating the mobilization of stored carbohydrates from the vegetative tissues to the grains, are of key importance for grain filling and grain yield. We used different inhibitors of plant hormone action to assess their effects on grain yield and on the expression of hormone-associated genes. Among the tested chemicals, 2-indol-3-yl-4-oxo-4-phenylbutanoic acid (PEO-IAA; antagonist of auxin receptor), nordihydroguaiaretic acid (NDGA; abscisic acid (ABA) biosynthesis inhibitor), and 2-aminoisobutyric acid (AIB; ethylene biosynthesis inhibitor) improved grain yield in a concentration dependent manner. These effects were also dependent on the plant developmental stage. NDGA and AIB treatments induced an increase in photosynthesis in flag leaves concomitant to the increments of starch content in flag leaves and grains. NDGA inhibited the expression of ABA-responsive gene, but did not significantly decrease ABA content. Instead, NDGA significantly decreased jasmonic acid and jasmonic acid-isoleucine. Our results support the notion that the specific inhibition of jasmonic acid and ethylene biosynthesis resulted in grain yield increase in rice.源库关系（sink/source relationships）调控储存碳水化合物从营养组织向籽粒的转运，对籽粒灌浆与籽粒产量至关重要。本研究采用多种植物激素作用抑制剂，探究其对籽粒产量及激素相关基因表达的影响。在所测试的化学试剂中，2-吲哚-3-基-4-氧代-4-苯基丁酸（PEO-IAA，生长素受体拮抗剂）、去二氢愈创木酸（NDGA，脱落酸（ABA）生物合成抑制剂）以及2-氨基异丁酸（AIB，乙烯生物合成抑制剂）均以浓度依赖的方式提升水稻籽粒产量。上述调控效应同时受植物发育阶段的影响。施加NDGA与AIB可提升剑叶的光合速率，同时伴随剑叶及籽粒中淀粉含量的增加。NDGA可抑制ABA响应基因的表达，但并未显著降低ABA含量；与之相反，NDGA可显著降低茉莉酸（jasmonic acid）及茉莉酸-异亮氨酸（jasmonic acid-isoleucine）的水平。本研究结果证实，特异性抑制茉莉酸与乙烯的生物合成可提升水稻籽粒产量。