Allelic variants of OsHKT1;1 underlie the divergence between indica and japonica subspecies of rice (Oryza sativa) for root sodium content.
Allelic variants of OsHKT1;1 underlie the divergence between indica and japonica subspecies of rice (Oryza sativa) for root sodium content.
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DOI：
10.1371/journal.pgen.1006823
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发表时间：
2017-06
期刊：
影响因子：
4.5
通讯作者：
Walia H
中科院分区：
文献类型：
--
作者：
Campbell MT;Bandillo N;Al Shiblawi FRA;Sharma S;Liu K;Du Q;Schmitz AJ;Zhang C;Véry AA;Lorenz AJ;Walia H
盐度是限制作物产量的一个主要因素。水稻（Oryza sativa）是世界上大多数地区的主要作物，对盐度胁迫高度敏感。为了发现水稻耐盐相关性状遗传变异的新来源，我们筛选了390个不同材料，在14天的中等（9 dS·m-1）盐度条件下进行筛选。在本研究中，芽部生长对中等盐度的响应与组织Na+含量无关。水稻主要亚群间根系Na+含量差异显著，籼稻品种根系Na+含量较高，粳稻品种根系Na+含量较低。通过全基因组关联（GWA）阐明了所观察到的表型变异的遗传基础。在4号染色体约575 Kb的区域，根Na+含量4 （root Na+ content 4, RNC4）中，根Na+:K+比值与根Na+含量的相关性最强。两个Na+转运蛋白，HKT1；1及HKT1；4个被确定为RNC4候选基因。两者HKT1表达减少；1及HKT1；4通过RNA干扰表明HKT1；1调控茎部和根部Na+含量，可能是RNC4的致病基因。HKT1内三个非同义突变；1在籼稻亚群中出现频率较高。当在非洲爪蟾卵母细胞中表达时，与日本爪蟾异构体相比，籼型优势异构体表现出更高的内向（负）电流和更低的内向整流电流激活的负电压阈值。引入包含HKT1的4.5kb片段；1启动子和CDS从一个籼稻品种转入粳稻背景，产生了与籼稻亚群相似的表型，具有较高的根Na+和Na+:K+。本研究提供证据证明HKT1；1调控根系Na+含量，是水稻两大亚种根系Na+含量差异的基础。尽管进行了深入的研究，但很少有基因被确定为水稻盐响应自然变异的基础。在本研究中，我们使用水稻多样性面板进行全基因组关联图谱鉴定HKT1；1是调节Na+分布的因子。在水稻多样性小组中，我们观察到籼稻亚群的根组织中Na+水平高于粳稻。在HKT1中发现了三个非同义变体；1与根组织中Na+积累的改变有关，并且在籼稻亚种和粳稻亚种之间表现出不同的频率。推出HKT1；从含有三个非同义变异体的籼稻加入到粳稻背景中，产生了与籼稻亚群相似的表型。这项工作表明，这些等位基因变异可能是在籼稻中观察到的较高根Na+的原因。本研究确定了Na+含量改良水稻的遗传资源，并提供了HKT1；1是籼稻和粳稻亚种根系Na+含量差异的基础。
Salinity is a major factor limiting crop productivity. Rice (Oryza sativa), a staple crop for the majority of the world, is highly sensitive to salinity stress. To discover novel sources of genetic variation for salt tolerance-related traits in rice, we screened 390 diverse accessions under 14 days of moderate (9 dS·m-1) salinity. In this study, shoot growth responses to moderate levels of salinity were independent of tissue Na+ content. A significant difference in root Na+ content was observed between the major subpopulations of rice, with indica accessions displaying higher root Na+ and japonica accessions exhibiting lower root Na+ content. The genetic basis of the observed variation in phenotypes was elucidated through genome-wide association (GWA). The strongest associations were identified for root Na+:K+ ratio and root Na+ content in a region spanning ~575 Kb on chromosome 4, named Root Na+ Content 4 (RNC4). Two Na+ transporters, HKT1;1 and HKT1;4 were identified as candidates for RNC4. Reduced expression of both HKT1;1 and HKT1;4 through RNA interference indicated that HKT1;1 regulates shoot and root Na+ content, and is likely the causal gene underlying RNC4. Three non-synonymous mutations within HKT1;1 were present at higher frequency in the indica subpopulation. When expressed in Xenopus oocytes the indica-predominant isoform exhibited higher inward (negative) currents and a less negative voltage threshold of inward rectifying current activation compared to the japonica-predominant isoform. The introduction of a 4.5kb fragment containing the HKT1;1 promoter and CDS from an indica variety into a japonica background, resulted in a phenotype similar to the indica subpopulation, with higher root Na+ and Na+:K+. This study provides evidence that HKT1;1 regulates root Na+ content, and underlies the divergence in root Na+ content between the two major subspecies in rice. Despite intensive research, few genes have been identified that underlie natural variation for salinity responses in rice. In this study, we used a rice diversity panel for genome wide association mapping to identify HKT1;1 as a factor regulating Na+ distribution. Within the rice diversity panel we observed higher Na+ levels in root tissue in the indica subpopulation compared to japonica accessions. Three non-synonymous variants were identified within HKT1;1 that were associated with altered Na+ accumulation in root tissue, and displayed contrasting frequencies between indica and japonica subspecies. The introduction of HKT1;1 from an indica accession that contained the three non-synonymous variants into a japonica background resulted in a phenotype similar to that exhibited by the indica subpopulation. This work suggests that these allelic variants are likely responsible for the higher root Na+ observed in indica accessions. This study has identified a genetic resource for modifying Na+ content rice, and provides evidence that HKT1;1 underlies the divergence between indica and japonica subspecies in root Na+ content.