Lee I, Foster KR, Morgan PW
Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843-2474
J Plant Growth Regul. 1998 Dec;17(4):185-195. doi: 10.1007/pl00007034.
CCC, uniconazol, ancymidol, prohexadione-calcium (BX-112), and CGA 163'935, which represent three groups of gibberellin (GA) biosynthesis inhibitors, were applied as a soil drench to Sorghum bicolor cultivars 58M (phyB-1, phytochrome B-deficient mutant) and 90M (phyB-2, equivalent phenotypically to wild type, PHYB, except for small differences in flowering dates). The inhibitors that block steps before GA12 (CCC, uniconazol, and ancymidol) lowered the concentrations of all endogenous early-C13alpha-hydroxylation pathway GAs found in sorghum: GA12, GA53, GA44, GA19, GA20, GA1, and GA8. In contrast, the inhibitors that block the conversion of GA20 --> GA1, (CGA 163'935 and BX-112) drastically reduced GA1 and GA8 levels, but they either did not change or caused accumulation of intermediates from GA12 to GA20. Combinations of pre-GA12 inhibitors and GA3 plus GA1 strongly reduced GAs other than GA1 and GA3. Each of these compounds inhibited shoot growth in both cultivars and delayed floral initiation in 90M. Floral initiation of 58M was also delayed by CCC, uniconazol, and ancymidol but not by CGA 163'935 and BX-112. This separation of shoot elongation from floral initiation in sorghum is novel. Both inhibition of shoot growth and delayed floral initiation were almost completely relieved by a mixture of GA3 and GA1 in both 58M and 90M. This observation, plus the much lower levels of endogenous GA3 than of GA1 observed in these experiments, implies that GA1 is the major endogenous GA active in shoot elongation. CGA 163'935 and BX-112 also failed to promote tillering in 58M, whereas inhibitors active before GA12 did so. The possibility that the GA20 --> GA1 inhibitors fail to block flowering and promote tillering in 58M because biosynthetic intermediates between GA12 and GA20 accumulate and/or because 58M is altered in GA metabolism in this same region of the biosynthetic pathway is discussed. Key Words. Gibberellin biosynthesis inhibitors-Phytochrome B-Flowering-Sorghum
多效唑、烯效唑、嘧啶醇、调环酸钙（BX - 112）和CGA 163935这三种赤霉素（GA）生物合成抑制剂，以土壤浇灌的方式施用于高粱品种58M（phyB - 1，phytochrome B缺失突变体）和90M（phyB - 2，除开花日期略有差异外，表型与野生型PHYB相同）。阻断GA12之前步骤的抑制剂（多效唑、烯效唑和嘧啶醇）降低了高粱中所有内源性早期C13α - 羟基化途径赤霉素的浓度：GA12、GA53、GA44、GA19、GA20、GA1和GA8。相比之下，阻断GA20向GA1转化的抑制剂（CGA 163935和BX - 112）大幅降低了GA1和GA8的水平，但它们要么没有改变GA12到GA20的中间产物水平，要么导致其积累。GA12之前的抑制剂与GA3加GA1的组合强烈降低了除GA1和GA3之外的赤霉素水平。这些化合物中的每一种都抑制了两个品种的茎生长，并延迟了90M的花期起始。多效唑、烯效唑和嘧啶醇也延迟了58M的花期起始，但CGA 163935和BX - 112没有。高粱中茎伸长与花期起始的这种分离是新颖的。在58M和90M中，GA3和GA1的混合物几乎完全缓解了茎生长的抑制和花期起始的延迟。这一观察结果，加上在这些实验中观察到的内源性GA3水平远低于GA1，意味着GA1是茎伸长中主要的内源性活性赤霉素。CGA 163935和BX - 112也未能促进58M的分蘖，而GA12之前有活性的抑制剂则可以。讨论了GA20向GA1转化的抑制剂未能阻断58M的开花并促进分蘖的可能性，原因是GA12和GA20之间的生物合成中间产物积累，和/或因为58M在生物合成途径的同一区域的GA代谢发生了改变。关键词：赤霉素生物合成抑制剂 - Phytochrome B - 开花 - 高粱
