秧苗富锌对不同水稻品种镉积累及相关转运基因的影响

【目的】 秧苗富锌是发挥水稻锌-镉拮抗效应的一种新模式,研究不同水稻品种对秧苗富锌降镉效应的响应差异及潜在机制,为该模式的推广应用奠定基础。【方法】 选择武运粳21号、浙粳优1578、黄华占、徽两优丝苗等4个品种开展水培富锌和盆栽验证试验,研究不同品种锌富集的动态特征及移栽后水稻组织对镉的吸收转运差异,通过分析根系相关镉转运基因的表达状况探究秧苗富锌降镉效应的种间差异机制。【结果】 锌培养对水稻秧苗的生长发育无明显影响,但不同品种幼苗锌富集能力差异明显,浙粳优1 578幼苗锌积累量（230 μg/株）最高,武运粳21号次之（124 μg/株）,黄华占和徽两优丝苗相对较低（85.1—95.0 μg/株）。浙粳优1578幼苗根系镉转运基因对富锌较为敏感,OsZIP7表达下调48.7%,OsZIP1表达上调81.3%;武运粳21号幼苗根系OsIRT1和OsZIP7表达分别下调35.9%和35.0%,OsZIP1表达上调31.1%;而黄华占和徽两优丝苗幼苗根系镉转运基因对富锌较不敏感。秧苗富锌使分蘖期武运粳21号根系和茎叶镉浓度分别下降26.7%和36.7%;浙粳优1578根系和茎叶镉浓度分别下降32.0%和40.0%,根系-茎叶镉转运系数显著下降12.0%。秧苗富锌使武运粳21号、浙粳优1578和黄华占糙米镉含量分别下降37.5%、36.7%和25.3%,而对徽两优丝苗糙米镉含量无明显影响,表明秧苗富锌对水稻降镉效应存在明显的种间差异。相关分析显示,糙米Cd浓度与茎叶Cd浓度呈显著正相关,而茎叶Cd浓度与根系和茎叶Zn浓度呈显著负相关,表明水稻内部Zn、Cd拮抗作用明显。根系和茎叶Zn浓度均与OsZIP7和OsIRT1的相对表达量呈显著负相关,与OsZIP1的相对表达量呈显著正相关关系,表明秧苗富锌主要通过调控根系OsZIP1、OsZIP7和OsIRT1的表达,从而间接影响糙米镉含量。【结论】 不同品种幼苗根系镉转运基因对富锌的响应差异明显,浙粳优1578和武运粳21号较为敏感,故而糙米镉含量下降幅度高于其他品种。

Effects of Seedlings Enriched with Zinc on Cadmium Accumulations and Related Transporter Genes Expressions in Different Rice Cultivars

【Objective】 Rice seedlings enriched with zinc (Zn) is a new method to antagonize cadmium (Cd) within rice, studying the various effects and underlying mechanisms among different rice cultivars is useful to provide a basis for the application of this method. 【Method】 Hydroponic and pot experiments were conducted to test the effects of the Zn enrichment in four cultivars including the Wuyunjing21, Zhejingyou1578, Huanghuazhan, and Huiliangyousimiao. Dynamics of Zn accumulation in different cultivars, and variations of Cd uptake and transport in rice tissues were investigated. Furthermore, the expressions of the Cd-related transporter genes of the root were analyzed to explore the underlying mechanisms responsible for the various effects in different cultivars. 【Result】 Results showed that the Zn cultivation didn’t affect the growth of all rice seedlings. Zn accumulations varied obviously among different cultivars, the Zhejingyou1578 had the highest Zn level (230 μg Zn per plant), followed by the Wuyunjing21 (124 μg Zn per plant), the Huanghuazhan and Huiliangyousimiao had the low levels (85.1-95.0 μg Zn per plant). Zn enrichment greatly influenced the expression of Cd-related transporters in the Zhejingyou1578, the OsZIP7 was down-regulated by 48.7% and OsZIP1 was up-regulated by 81.3%. The expressions of the OsIRT1 and OsZIP7 in the Wuyunjing21 were also down-regulated by 35.9% and 35.0%, respectively, and the OsZIP1 was up-regulated by 31.1%. However, the Cd-related transporters in the Huanghuazhan and Huiliangyousimiao were insensitive to Zn enrichment. As a result, Zn enrichment significantly reduced Cd concentrations in the root and shoot by 26.7% and 36.7% of the Wuyunjing21, and 32.0% and 40.0% of the Zhejingyou1578 with a 12.0% inhibition on the Cd transport, respectively. Furthermore, brown rice Cd were reduced by 37.5%, 36.7% and 25.3% in the Wuyunjing21, Zhejingyou1578, and Huanghuazhan, respectively, while no difference occurred in the Huiliangyousimiao, revealing various effects on reducing Cd among different cultivars induced by the Zn enrichment. Correlation analysis showed that the brown rice Cd was negatively correlated with the shoot Cd which was negatively correlated with the root and shoot Zn, revealing a significant antagonism between Zn and Cd within rice. However, the root and shoot Zn were negatively correlated with the OsZIP7 and OsIRT1 and positively correlated with the OsZIP1 expression, indicating that the Zn enrichment within seedlings influenced the brown rice Cd mainly through regulating the expressions of the OsZIP1, OsZIP7 and OsIRT1. 【Conclusion】 The regulations on Cd-related transporters through Zn enrichment were varied among different cultivars, and the Zhejingyou1578 and Wuyunjing21 were more sensitive, so that the reductions of brown rice Cd were higher than other cultivars.