籽粒建成期高温胁迫影响糯玉米籽粒胚乳发育的生理机制

Global warming is inevitable, and high temperature (>35°C) is normal phenomenon during summer in Southern China. Our group clarified the effects of heat stress during grain filling on the grain starch structure and property of waxy maize and ascertained that the grain yield and starch quality was seriously affected by grain formation stage in the past 7 years . The projects will analysis the types (day high temperature stress, night temperature stress, and day and night temperature stress) and degrees of heat stress at grain formation stage on morphology, size, quantity and distribution of the grain endosperm cell and amyloplast. The discrepancy locus of protein expression under heat stress was identified by isobaric tags for relative and absolute quantitation technology. The differential expressions of gene involved in grain development, grain component metabolism, adversity response were analyzed by real-time fluorescence quantitative PCR. The grain filling parameters, activities involved in starch, sugar and protein synthesis, starch structure and property were studied. In field production, by adjust sowing dates, the daily maximum, minimum, and average temperature during grain filling on grain endosperm development was clarified and to verify the pots research results. By clarification the physiological and biochemical mechanism of grain endosperm development to heat stress, the results could afford theoretical basis for anti-adversity and improve quality cultivation in the warming conditions for waxy maize production in the future.

大气温度升高不可避免，高温（>35℃）在中国南方夏季已成为一种常态。课题组前期阐明了结实期高温胁迫对糯玉米籽粒淀粉结构和品质的影响，并明确了籽粒建成期是影响籽粒产量和淀粉品质形成的关键时期。项目拟在前期研究的基础上，深入分析籽粒建成期高温胁迫类型(昼高温、夜高温、昼夜高温)和高温胁迫程度对糯玉米籽粒胚乳细胞和淀粉体形态、大小、数量和分布的影响，利用同位素相对标记与绝对定量技术进行蛋白质组学鉴定，明确高温胁迫下蛋白表达的差异位点，利用实时荧光定量PCR技术分析与籽粒生长发育、组分代谢、逆境响应等基因的表达差异，并分析籽粒灌浆特征，淀粉、糖和蛋白质合成相关酶活性，籽粒淀粉结构和品质。大田生产中通过播期调整，分析结实期日最高温度、最低温度和平均温度对籽粒胚乳发育的影响，验证盆栽试验结果。明确高温胁迫影响糯玉米籽粒胚乳发育的生理生化机制，为糯玉米在温度升高条件下的抗逆优质栽培提供理论支撑。

气候变暖不可逆转，高温胁迫呈重发频发和常态化趋势。本研究以热敏型苏玉糯5号和耐热型渝糯7号材料，研究了籽粒建成期不同类型、不同程度、不同持续时间高温胁迫对糯玉米胚乳发育和淀粉品质的影响及其生理机制。结果表明，不同类型高温胁迫均抑制了籽粒胚乳细胞发育，表现为胚乳细胞和淀粉体数量变小、体积增大，籽粒发育加快、灌浆终止提前、淀粉积累受限，其主要原因是高温胁迫抑制了淀粉合成相关酶活性，生长素含量降低、脱落酸含量升高。多组学（蛋白质组、代谢组和转录组）分析表明，生长素、脱落酸和水扬酸信号通路相关基因和蛋白表达参与调控胚乳淀粉发育和品质形成，以昼夜高温的影响最大，其次是昼高温，表明昼间光合合成能力的降低对胚乳发育的影响大于夜间呼吸消耗增加的影响。不同高温胁迫程度(T0：28℃/20℃，T1：32℃/24℃，T2：36℃/28℃，T3：40℃/32℃)下，与T0相比，T1对胚乳淀粉发育影响较小，T2和T3影响较大，且T3对胚乳淀粉合成相关酶活性和籽粒充实动态的影响最为严重，淀粉黏度最低、回生最高。籽粒发育和淀粉积累随着高温胁迫时间的延长而加剧，但中后期淀粉合成相关酶活性在两个高温胁迫时间（授粉后2-6d和2-11d）下无显著差异。不同播期中，早播（6月11日）处理下植株在开花和籽粒灌浆初期温度显著高于适播（7月1日）和迟播（7月21日）处理，表现为粒径较大、长链比例最多，不同播期中以适播处理下的籽粒产量较高，淀粉品质较优，但应防止过分推迟播期造成后期低温冷害。项目也发现了合理施肥或吐丝期喷施外源生长调节剂可缓解结实期高温胁迫对糯玉米产量和淀粉品质的影响。总体上，项目明确了高温胁迫类型、程度和持续时间对糯玉米淀粉结构和功能和影响，并利用多组学手段阐明了高温胁迫类型下淀粉合成和内源激素相关基因和蛋白表达参与淀粉胚乳发育和淀粉形成的分子生物学机理，为温度升高条件下的糯玉米品质调优提供了理论指导，播期试验结果为南方地区糯玉米生产的适期播种保证高产优质提供了参考依据。