Boyer J S, Westgate M E
College of Marine Studies, University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA.
J Exp Bot. 2004 Nov;55(407):2385-94. doi: 10.1093/jxb/erh219. Epub 2004 Jul 30.
Plant reproduction is sensitive to water deficits, especially during the early phases when development may cease irreversibly even though the parent remains alive. Grain numbers decrease because of several developmental changes, especially ovary abortion in maize (Zea mays L.) or pollen sterility in small grains. In maize, the water deficits inhibit photosynthesis, and the decrease in photosynthate flux to the developing organs appears to trigger abortion. Abscisic acid also increases in the parent and may play a role, perhaps by inhibiting photosynthesis through stomatal closure. Recent work indicates that invertase activity is inhibited and starch is diminished in the ovaries or affected pollen. Also, sucrose fed to the stems rescues many of the ovaries otherwise destined to abort. The feeding restores some of the ovary starch and invertase activity. These studies implicate invertase as a limiting enzyme step for grain yields during a water deficit, and transcript profiling with microarrays has identified genes that are up- or down-regulated during water deficit-induced abortion in maize. However, profiling studies to date have not reported changes in invertase or starch synthesizing genes in water-deficient ovaries, perhaps because there were too few sampling times. The ovary rescue with sucrose feeding indicates either that the changes identified in the profiling are of no consequence for inhibiting ovary development or that gene expression reverts to control levels when the sugar stream recovers. Careful documentation of tissue- and developmentally specific gene expression are needed to resolve these issues and link metabolic changes to the decreased sugar flux affecting the reproductive organs.
植物繁殖对水分亏缺很敏感，尤其是在早期阶段，此时即使亲本仍然存活，发育也可能不可逆转地停止。由于多种发育变化，籽粒数量会减少，特别是玉米（Zea mays L.）的子房败育或小粒作物的花粉不育。在玉米中，水分亏缺会抑制光合作用，光合产物向发育中器官的通量减少似乎会引发败育。脱落酸在亲本中也会增加，可能通过气孔关闭抑制光合作用而发挥作用。最近的研究表明，子房或受影响的花粉中的转化酶活性受到抑制，淀粉含量减少。此外，给茎部饲喂蔗糖能挽救许多原本注定要败育的子房。饲喂能恢复一些子房淀粉和转化酶活性。这些研究表明，转化酶是水分亏缺期间籽粒产量的限制酶步骤，利用微阵列进行的转录谱分析已经确定了玉米水分亏缺诱导败育期间上调或下调的基因。然而，迄今为止的谱分析研究尚未报道水分亏缺的子房中转化酶或淀粉合成基因的变化，可能是因为采样时间太少。用蔗糖饲喂挽救子房表明，谱分析中确定的变化对抑制子房发育没有影响，或者当糖流恢复时基因表达会恢复到对照水平。需要仔细记录组织和发育特异性基因表达，以解决这些问题，并将代谢变化与影响生殖器官的糖通量减少联系起来。
