Kilasi Newton Lwiyiso, Singh Jugpreet, Vallejos Carlos Eduardo, Ye Changrong, Jagadish S V Krishna, Kusolwa Paul, Rathinasabapathi Bala
Horticultural Sciences Department, University of Florida, Gainesville, FL, United States.
Department of Crop Science and Production, Sokoine University of Agriculture, Morogoro, Tanzania.
Front Plant Sci. 2018 Nov 1;9:1578. doi: 10.3389/fpls.2018.01578. eCollection 2018.
Productivity of rice, world's most important cereal is threatened by high temperature stress, intensified by climate change. Development of heat stress-tolerant varieties is one of the best strategies to maintain its productivity. However, heat stress tolerance is a multigenic trait and the candidate genes are poorly known. Therefore, we aimed to identify quantitative trait loci (QTL) for vegetative stage tolerance to heat stress in rice and the corresponding candidate genes. We used genotyping-by-sequencing to generate single nucleotide polymorphic (SNP) markers and genotype 150 F recombinant inbred lines (RILs) obtained by crossing heat tolerant "N22" and heat susceptible "IR64" varieties. A linkage map was constructed using 4,074 high quality SNP markers that corresponded to 1,638 recombinationally unique events in this mapping population. Six QTL for root length and two for shoot length under control conditions with 2.1-12% effect were identified. One QTL was identified for "root length under heat stress," with 20.4% effect. Four QTL were identified for "root length under heat stress as percent of control" that explained the total phenotypic variation from 5.2 to 8.6%. Three QTL with 5.3-10.2% effect were identified for "shoot length under heat stress," and seven QTL with 6.6-19% effect were identified for "shoot length under heat stress expressed as percentage of control." Among the QTL identified six were overlapping between those identified using shoot traits and root traits: two were overlapping between QTL identified for "shoot length under heat stress" and "root length expressed as percentage of control" and two QTL for "shoot length as percentage of control" were overlapping a QTL each for "root length as percentage of control" and "shoot length under heat stress." Genes coding 1,037 potential transcripts were identified based on their location in 10 QTL regions for vegetative stage heat stress tolerance. Among these, 213 transcript annotations were reported to be connected to stress tolerance in previous research in the literature. These putative candidate genes included transcription factors, chaperone proteins (e.g., alpha-crystallin family heat shock protein 20 and DNAJ homolog heat shock protein), proteases, protein kinases, phospholipases, and proteins related to disease resistance and defense and several novel proteins currently annotated as expressed and hypothetical proteins.
水稻是世界上最重要的谷类作物，其产量受到高温胁迫的威胁，而气候变化加剧了这种胁迫。培育耐热品种是维持其产量的最佳策略之一。然而，耐热性是一个多基因性状，相关候选基因鲜为人知。因此，我们旨在鉴定水稻营养生长期耐热性的数量性状位点（QTL）及其相应的候选基因。我们采用简化基因组测序来生成单核苷酸多态性（SNP）标记，并对通过耐热品种“N22”与热敏感品种“IR64”杂交获得的150个F重组自交系（RIL）进行基因分型。利用4074个高质量SNP标记构建了一个连锁图谱，这些标记对应于该作图群体中的1638个重组独特事件。在对照条件下，鉴定出6个影响根长的QTL和2个影响地上部长度的QTL，贡献率为2.1%-12%。鉴定出1个影响“热胁迫下根长”的QTL，贡献率为20.4%。鉴定出4个影响“热胁迫下根长占对照的百分比”的QTL，解释了5.2%-8.6%的总表型变异。鉴定出3个影响“热胁迫下地上部长度”的QTL，贡献率为5.3%-10.2%；鉴定出7个影响“热胁迫下地上部长度占对照的百分比”的QTL，贡献率为6.6%-19%。在鉴定出的QTL中，有6个在利用地上部性状和根性状鉴定出的QTL之间重叠：2个在“热胁迫下地上部长度”和“根长占对照的百分比”鉴定出的QTL之间重叠，2个“地上部长度占对照的百分比”的QTL分别与“根长占对照的百分比”和“热胁迫下地上部长度”的一个QTL重叠。根据10个营养生长期耐热性QTL区域内的位置，鉴定出编码1037个潜在转录本的基因。其中，213个转录本注释据文献中先前的研究报道与胁迫耐受性相关。这些推定的候选基因包括转录因子、伴侣蛋白（如α-晶状体蛋白家族热休克蛋白20和DNAJ同源热休克蛋白）、蛋白酶、蛋白激酶、磷脂酶以及与抗病和防御相关的蛋白，还有一些目前注释为表达蛋白和假定蛋白的新蛋白。
