Suppression of α‐amylase genes improves quality of rice grain ripened under high temperature

High temperature impairs rice (Oryza sativa) grain filling by inhibiting the deposition of storage materials such as starch, resulting in mature grains with a chalky appearance, currently a major problem for rice farming in Asian countries. Such deterioration of grain quality is accompanied by the altered expression of starch metabolism‐related genes. Here we report the involvement of a starch‐hydrolyzing enzyme, α‐amylase, in high temperature‐triggered grain chalkiness. In developing seeds, high temperature induced the expression of α‐amylase genes, namely Amy1A, Amy1C, Amy3A, Amy3D and Amy3E, as well as α‐amylase activity, while it decreased an α‐amylase‐repressing plant hormone, ABA, suggesting starch to be degraded by α‐amylase in developing grains under elevated temperature. Furthermore, RNAi‐mediated suppression of α‐amylase genes in ripening seeds resulted in fewer chalky grains under high‐temperature conditions. As the extent of the decrease in chalky grains was highly correlated to decreases in the expression of Amy1A, Amy1C, Amy3A and Amy3B, these genes would be involved in the chalkiness through degradation of starch accumulating in the developing grains. The results show that activation of α‐amylase by high temperature is a crucial trigger for grain chalkiness and that its suppression is a potential strategy for ameliorating grain damage from global warming.     

Incorporating rhizosphere processes into field-scale (agro)ecosystem models

Three different strategies for incorporating rhizosphere processes within field-scale models are compared, taking triple-cropped irrigated rice production as a common system and CH₄ emission as a common focus of interest. The strategies may be characterised as homogeneous (model I; root C deposition is added to the bulk soil compartment), areal (model II; roots contribute via aerenchymatous exchange to an increased soil–atmosphere interfacial surface area), and volumetric (model III; roots create around themselves a specific rhizosphere compartment). Model I is simpler than model II, which is simpler than model III. With identical parameters all models lead to similar seasonally integrated CH₄ emissions, but when the pattern of emission and the simulated CH₄ concentration in the soil is brought into the reckoning, the following order of precedence (greater is better) becomes clear: model IIImodel II>model I. Current field-scale models of soil organic matter (SOM) transformation, especially in rice soils, could be improved by taking explicit account of the rhizosphere and the processes which occur within it.     

水稻矮杆多分蘖突变体CA648的光合生理特性分析

本研究分析了水稻矮杆多分蘖突变体丛矮648 (CA648)及对照中花11 (ZH11)在分蘖期叶片的叶绿素含量、光合速率,还原糖、蔗糖含量以及POD酶活力。结果表明,分蘖期ZH11剑叶中叶绿素含量高于CA648。水稻分蘖前期,CA648的净光合速率、气孔导度、蒸腾速率都低于ZH11,胞间CO2浓度高于ZH11;而在分蘖盛期(分蘖期后20 d)两种材料的净光合速率差异显著,ZH11净光合速率比CA648高17.5%,同时CA648的气孔导度、胞间CO2浓度和蒸腾速率都低于ZH11;而分蘖后期ZH11与CA648净光合速率几乎相同。分蘖盛期CA648叶片还原糖含量明显比对照高;而茎杆还原糖含量与对照无差异。CA648叶片蔗糖含量低于对照,约为ZH11的77.5%;而茎杆的蔗糖含量高于对照,比ZH11高30.7%。两种材料POD酶活力差异明显,其中在分蘖盛期,CA648叶、茎中的POD酶活力分别比ZH11高73.0%、16.8%。     

水稻根系响应镉胁迫的蛋白质差异表达

为探讨水稻根系对镉胁迫的分子生理响应,以抗镉水稻PI312777和镉敏感水稻IR24为材料,设置Cd~(2+)浓度为0、50和100μmol/L的水培试验,处理7 d后分析了水稻根系的蛋白质差异表达。结果表明,在镉胁迫下水稻PI312777和IR24根系有18个蛋白质发生了差异表达,其中的12个得到MALDI-TOF/MS鉴定。这些鉴定的蛋白功能可分四类:(1)与活性氧(ROS)胁迫相关的过氧化物酶(POD)、蛋氨酸腺苷转移酶(MAT)、类萌发素蛋白前体;(2)与谷胱甘肽(GSH)合成相关的S-腺苷甲硫氨酸合成酶(SAMS)、谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH);(3)与逆境胁迫相关的ABA胁迫诱导蛋白含HVA22域蛋白、ABA-胁迫-成熟诱导蛋白5(ASR5);(4)与细胞分裂调控相关的GTP结合核蛋白Ran-2。镉胁迫下SAMS和GTP结合核蛋白Ran-2在两种水稻根系均发生上调表达;MAT、POD、类萌发素蛋白前体和GS发生下调表达;依赖NADP-GDH、GDH和磷酸甘油酸变位酶在IR24根部均发生下调表达,在PI312777根部仅在100μmol/L Cd~(2+)处理发生下调表达;含HVA22域蛋白在PI312777根部上调表达,在IR24根部发生下调表达;ASR5在PI312777根部上调表达,在IR24根部的表达无显著差异;100μmol/L Cd~(2+)胁迫下60S酸性核糖体蛋白P0在水稻PI312777根部表达下调,在IR24根部表达上调。可见,镉胁迫使水稻根部ROS增加,形成氧化胁迫反应,造成毒害作用,而水稻根通过调节SAMS和GS提高GSH合成降低镉毒害。ASR5和HVA22蛋白等逆境胁迫蛋白的表达差异则是水稻品种间抗性差异的重要原因之一。     

The auxin transporter,OsAUX1, is involved in primary root and root hair elongation and in Cd stress responses in rice (Oryza sativa L.)

Auxin and cadmium (Cd) stress play critical roles during root development. There are only a few reports on the mechanisms by which Cd stress influences auxin homeostasis and affects primary root (PR) and lateral root (LR) development, and almost nothing is known about how auxin and Cd interfere with root hair (RH) development. Here, we characterize rice osaux1 mutants that have a longer PR and shorter RHs in hydroponic culture, and that are more sensitive to Cd stress compared to wild‐type (Dongjin). OsAUX1 expression in root hair cells is different from that of its paralogous gene, AtAUX1, which is expressed in non‐hair cells. However, OsAUX1, like AtAUX1, localizes at the plasma membrane and appears to function as an auxin tranporter. Decreased auxin distribution and contents in the osaux1 mutant result in reduction of OsCyCB1;1 expression and shortened PRs, LRs and RHs under Cd stress, but may be rescued by treatment with the membrane‐permeable auxin 1‐naphthalene acetic acid. Treatment with the auxin transport inhibitors 1‐naphthoxyacetic acid and N‐1‐naphthylphthalamic acid increased the Cd sensitivity of WT rice. Cd contents in the osaux1 mutant were not altered, but reactive oxygen species‐mediated damage was enhanced, further increasing the sensitivity of the osaux1 mutant to Cd stress. Taken together, our results indicate that OsAUX1 plays an important role in root development and in responses to Cd stress.     

气候变化对黑龙江省水稻障碍型冷害的影响

明确气候变化对黑龙江省水稻孕穗期和抽穗期障碍型冷害的影响,可为水稻安全生产提供科学依据。基于黑龙江省70个台站1971—2012年的气象资料和10个台站1980—2011年水稻生育期数据,结合水稻障碍型冷害指标,分析了气候变化对黑龙江省水稻障碍型冷害的影响。结果表明:(1)水稻孕穗期障碍型冷害1990s发生频率最低,2000s发生频率最高;抽穗期障碍型冷害1970s和1980s发生频率高,1990s和2000s发生频率低。(2)抽穗期障碍型冷害发生程度大于孕穗期障碍型冷害。(3)不同熟型水稻品种可种植北界逐渐北移东扩,极早熟、早熟和中熟品种可种植范围分别缩小了5、21和11个县(市),中晚熟和晚熟品种可种植范围分别扩大了14和23个县(市)。(4)随着水稻种植格局的变化,不同熟型水稻障碍型冷害均在1990s发生频率最低,2000s发生频率最高。     

水稻短根突变体Osksr5的遗传分析和基因定位

水稻根系对其生长、发育及产量等起着至关重要的作用。该研究从甲基磺酸乙酯（ethyl methane sulfonate,EMS）诱变的籼稻Kasalath突变体库中筛选到1个根系变短的突变体,命名为Osksr5（Oryza sativa kasalath short root 5）,该突变体植株具体表现为主根、不定根和侧根都明显变短,不定根的数目相对减少,株高与野生型相比也明显矮小。遗传分析结果表明,该突变性状由1对隐性核基因控制。利用图位克隆技术将OsKSR5基因定位在第1染色体的STS（sequence tagged site）分子标记33027k和33471k,物理距离约为444 kb。对OsKSR5基因的定位为进一步克隆该基因和阐明水稻根系发育的分子机理奠定了基础。