OsMYB84,a transcriptional regulator of OsCOPT2 and OsHMA5,modulates copper uptake and transport and yield production in rice

Transcription factors regulating crop uptake and translocation of the micronutrient Cu have not been identified.We isolated a novel R2R3-MYB transcription factor,OsMYB84,and showed that it was a positive regulator involved in uptake and transport of Cu via activation of OsCOPT2 and OsHMA expression.OsMYB84 was highly expressed in roots and anthers and induced by Cu.Overexpression of OsMYB84 promoted uptake and root-to-shoot translocation of Cu in rice,facilitated Cu distribution into grain and increased grain yield.In contrast,mutation of OsMYB84 reduced Cu concentration in xylem sap.OsMYB84 bound to the promoter region of OsCOPT2 and OsHMA5 and upregulated their expression.OsCOPT2 mutants showed reduced uptake of Cu and OsHMA5 overexpression lines showed increased root-to-shoot translocation of Cu.

Rice Heavy Metal P-type ATPase OsHMA6 Is Likely a Copper Efflux Protein

P1B-type heavy metal ATPases(HMAs)are transmembrane metal-transporting proteins that play a key role in metal homeostasis.We here reported the characterization of rice OsHMA6,a member of the P1B-type ATPase family.Phylogenetic tree analysis showed that OsHMA6 belonged to the Cu/Ag subgroup of the HMA family and had a close evolutionary relationship with OsHMA9.Amino acid sequence alignment showed 82.78%consistency between OsHMA6 and OsHMA9.OsHMA6 expressed in all organs at different growth stages,including spikelet,and abundant in leaf blades,however,OsHMA9 most strongly expressed in roots,but very low in spikelet.Excessive Cu^2+can up-regulate the expression of OsHMA6 and OsHMA9 in rice seedlings.The heterologous expression in yeast showed that OsHMA6 can significantly rescue the growth of yeast strain CM52 when supplied with 3 or 6 mmol/L Cu^2+.Compared with the empty vector pYES2,the Cu concentration in OsHMA6-pYES2 decreased by 23.4%and 30.3%under 3 or 6 mmol/L Cu2+,respectively.Subcellular localization revealed that OsHMA6 was located in the plasma membrane.These results suggested that OsHMA6,similar to OsHMA9,is likely a copper efflux protein located in the plasma membrane.

光照时间对不同镉耐受水稻品种镉积累的影响

【目的】品种性状和环境因素均影响水稻对镉(Cd)的积累,通过分析不同光照时间下不同镉耐受品种水稻的生长及Cd积累和分配,为调控水稻Cd积累提供技术参考。【方法】采用水培试验方法,供试材料为两个高Cd积累品种‘玉针香’、‘湘晚籼12号’和1个Cd吸收主效基因Nramp5缺失品种‘韶香100’。营养液中添加1μmol/L Cd模拟Cd胁迫条件,设置光照/黑暗为12 h/12 h、16 h/8 h两个光照处理。在分蘖期调查水稻植株生长指标、各部位Cd含量、亚细胞各成分(细胞壁、细胞器、可溶性部分)中Cd含量与分配,以及Cd主要吸收、转运基因表达的差异。【结果】与光照12 h相比,光照16 h各水稻品种的SPAD值显著上升,‘玉针香’株高显著降低,而‘湘晚籼12号’和‘韶香100’株高则显著增加;3个品种根体积和根干重均降低;各品种水稻地上部和根部Cd含量提高,反映在亚细胞水平上,‘玉针香’品种细胞壁和细胞器内Cd含量显著上升,而细胞可溶性部分Cd含量显著下降,而‘韶香100和’‘湘晚籼12号’各亚细胞组分的Cd含量均增加。相比于光照12 h,光照16 h下‘玉针香’地上部中Cd吸收基因OsNramp5表达水平上调,而‘湘晚籼12号’OsNramp5表达水平下调;负责液泡Cd富集的基因OsHMA3在‘玉针香’和‘韶香100’两品种中表达上调,在‘湘晚籼12号’中表达下调。【结论】无论品种是否耐受Cd,延长光照时间可显著降低Cd胁迫下水稻根系的生长发育,提高水稻体内的Cd含量。不同Cd积累特性品种亚细胞成分中Cd的分配差异受吸收和运转基因调控,并由此导致Cd胁迫下植株地上部和根部生长的差异。延长光照时间导致同一Cd吸收分配调节基因在不同水稻品种表达的差异及其作用还需进一步研究。

类重金属ATP酶基因序列遗传变异分析

OsHMA2是水稻根和地上部一个主要的Zn和Cd的转运蛋白,在水稻基因组OsHMA2位点存在OsHMA2类似基因OsHMA2-like,编码蛋白包含水稻P1B型ATP酶重金属转运蛋白的功能域。对来自世界不同稻区的27份亚洲栽培稻和8份野生稻基因OsHMA2-like编码区序列进行了测序分析,以了解水稻OsHMA2-like序列的多样性,为发掘基因资源提供信息。OsHMA2-like核苷酸序列和氨基酸序列分析表明,在471bp的编码序列内发现了6个变异位点;Tajima'sD检验表明均不显著,说明这些位点属中性进化状态;6个变异位点中,第15、78、132、214、417位点碱基不引起氨基酸的变异,而第457位的变异使得5个供试材料(1个O.nivara,4个ARO品种和1个粳稻品种)由于提前形成终止子在C末端少3个氨基酸,ARO类品种在此位点上与TRJ、IND、TEJ存在显著差异,这暗示ARO类品种可能由O.nivara演化而来。

浅析危害辨识、风险评价和风险控制的审核方法

本文针对OSHMS审核员对用人单位建立和保持危害辨识、风险评价和风险控制程序的审核,浅析进行危害辨识、风险评价和风险控制过程的审核方法和途径,确保审核的合理性、充分性与有效性。