低植酸水稻高温花粉败育及其结实障碍形成的热害机理探析

The reduction of grain phytic acid (PA), aiming to exploit low phytic acid (lpa) crops, has widely been considered as an effective strategy to improve the rice nutritional quality in recent years. However, lpa rice, with sharply lowering grain PA concentration, is generally characterized by inferior spikelet sterility and poor grain plumpness compare to its wild-type, thus lpa lines were more susceptible to stressful growth environment, especially at its reproductive growth period. To solve the contradiction between the quality improvement and their inferior agronomic performance (e.g high susceptibility to stressful growth condition) for lpa rice, three lpa rice lines (both radiation-induced and transgenic-induced) were employed to clarify the effects of stressful high temperature at reproductive stage on floral injury, spikelet sterility, seed setting rate and other related eco-physiological characteristics. Furthermore, we analyzed the gene expression profiles related to inositol phosphates synthesis and sugar transport by using fluorescence quantitative PCR and micro-array, key metabolic enzyme activity, chemical compositions, ATPase activity and sugar sub-organ distribution in anther and pollen organ under high temperature at reproductive stage. These results shall illustrate the metabolic characteristics and regulatory mechanism of floral injury and pollen fertility susceptibility responding to stressful high temperature for lpa rice, and may clarify the underlying mechanism of the pollen abortion and seed-setting obstacles as induced by high temperature for lpa rice.

降低水稻等农作物籽粒中的植酸含量是近年来作物营养品质改良工作的一个重要目标，但伴随作物籽粒植酸含量的下降，低植酸作物在生殖生长阶段的结实特性和环境生态适应性却明显变劣。本项目针对作物品质改良与其产量性状及抗逆能力变差之间的这一矛盾关系，以低植酸水稻为材料，通过在水稻孕穗至抽穗期间的高温处理试验，探讨高温胁迫对低植酸水稻花器伤害、花粉育性与结实特性影响的生态生理特点；在此基础上，通过对高温胁迫下发育花药器官和成熟花粉粒中的肌醇磷酸代谢和糖类营养物质转运等相关代谢途径若干重要功能基因转录表达的荧光定量PCR和微阵列检测，并结合有关代谢环节的关键酶活性和相关化学组分测定，以及发育花药中ATP酶活性与糖类物质积累变化的亚器官分布观察，以揭示高温胁迫对低植酸水稻花器伤害和花粉育性影响的生理代谢特点及其调控机制，探明高温胁迫导致花粉败育及其结实障碍形成的主要生理症结。

降低水稻等作物籽粒中的植酸含量是近年来作物营养品质改良工作的一个重要目标，但低植酸作物生育后期的高温胁迫结实障碍问题更严重。本项目以低植酸水稻突变体与耐热性状存在明显差异的水稻品种为材料，通过水稻孕穗至抽穗期间的高温处理试验（高温胁迫程度与高温胁迫持续时间），对低植酸水稻在不同温度处理下的花粉育性和结实性状及其高温敏感性进行了检测分析，并结合水稻发育花药器官中的磷酸肌醇与糖类物质组分测定、ROS分布与钙离子荧光观察，以及相关代谢路径及其调节信号的检测鉴定，探析了低植酸水稻高温花粉败育及其结实障碍形成的生理生态机制。主要研究结果如下：1）减数分裂期高温胁迫会引起水稻发育花药器官ROS水平上升、已糖/蔗糖比下降和无机磷含量增加。与对照品种相比，低植酸水稻遭遇高温后的变化（上升或下降）程度更明显，这是低植酸水稻高温结实障碍形成的一个重要生态特征；2）高温胁迫在引起水稻花药器官中的肌醇磷酸IP3-6组分含量降低和PLC等肌醇磷酸代谢途径重要功能基因表达量显著降低的同时，可抑制花药组织中IP3-Ca2+信号的正常传递，使发育花药器官的热胁迫响应受阻和内质网热胁迫损伤加剧；3）高温胁迫会引起水稻花药器官产生Ca2+内涌现象，增强OsRBOHB的转录及其蛋白表达，激发ROS产生和过氧化损伤；4）高温胁迫引起花药壁的蔗糖含量上升、腔液和花粉粒中的蔗糖含量下降，使花药器官中的蔗糖卸载与转运代谢受到抑制，进而造成发育花粉里的淀粉积累量不足,低植酸水稻的此生理调控过程与其花药器官中的果糖磷酸激酶（FRK）和已糖磷酸激酶（HXK）关系密切。