Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, P.R. China ; Guangdong Provincial Key Laboratory of New Technology in Rice Breeding, Guangzhou, P.R. China.
PLoS One. 2013 Aug 30;8(8):e73886. doi: 10.1371/journal.pone.0073886. eCollection 2013.
Hybrid weakness (HW) is an important postzygotic isolation which occurs in both intra- and inter-specific crosses. In this study, we described a novel low temperature-dependent intrasubspecific hybrid weakness in the F1 plants derived from the cross between two indica rice varieties Taifeng A and V1134. HW plants showed growth retardation, reduced panicle number and pale green leaves with chlorotic spots. Cytological assay showed that there were reduced cell numbers, larger intercellular spaces, thicker cell walls, and abnormal development of chloroplast and mitochondria in the mature leaves from HW F1 plants in comparison with that from both of the parental lines. Genetic analysis revealed that HW was controlled by two complementary dominant genes Hw3 from V1134 and Hw4 from Taifeng A. Hw3 was mapped in a 136 kb interval between the markers Indel1118 and Indel1117 on chromosome 11, and Hw4 was mapped in the region of about 15 cM between RM182 and RM505 on chromosome 7, respectively. RT-PCR analysis revealed that only LOC_Os11g44310, encoding a putative calmodulin-binding protein (OsCaMBP), differentially expressed among Taifeng A, V1134 and their HW F1. No recombinant was detected using the markers designed based on the sequence of LOC_Os11g44310 in the BC1F2 (Taifeng A//Taifeng A/V1134) population. Hence, LOC_Os11g44310 was probably the candidate gene of Hw3. Gene amplification suggested that LOC_Os11g44310 was present in V1134 and absent in Taifeng A. BLAST search revealed that LOC_Os11g44310 had one copy in the japonica genomic sequence of Nipponbare, and no homologous sequence in the indica reference sequence of 9311. Our results indicate that Hw3 is a novel gene for inducing hybrid weakness in rice.
杂种弱势（HW）是一种重要的合子后隔离现象，发生在种内和种间杂交中。在这项研究中，我们描述了来自两个籼稻品种泰丰 A 和 V1134 杂交的 F1 植物中一种新的低温依赖的亚种内杂种弱势。HW 植株表现出生长迟缓、穗数减少、叶片浅绿色并有黄化斑点。细胞学分析表明，与亲本系相比，HW F1 植株的成熟叶片中细胞数量减少、细胞间隙增大、细胞壁变厚，叶绿体和线粒体发育异常。遗传分析表明，HW 由 V1134 的两个互补显性基因 Hw3 和泰丰 A 的 Hw4 控制。Hw3 被定位在第 11 号染色体上的标记 Indel1118 和 Indel1117 之间的 136kb 区间内，Hw4 被定位在第 7 号染色体上的 RM182 和 RM505 之间约 15cM 的区域内。RT-PCR 分析表明，只有 LOC_Os11g44310 在泰丰 A、V1134 和它们的 HW F1 之间差异表达，该基因编码一种假定的钙调素结合蛋白（OsCaMBP）。在 BC1F2（泰丰 A//泰丰 A/V1134）群体中，使用基于 LOC_Os11g44310 序列设计的标记未检测到重组。因此，LOC_Os11g44310 可能是 Hw3 的候选基因。基因扩增表明 LOC_Os11g44310 存在于 V1134 中，而不存在于泰丰 A 中。BLAST 搜索表明 LOC_Os11g44310 在粳稻基因组序列 Nipponbare 中有一个拷贝，而在籼稻参考序列 9311 中没有同源序列。我们的结果表明，Hw3 是一个诱导水稻杂种弱势的新基因。
