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A Novel Combination of Genes Causing Temperature-Sensitive Hybrid Weakness in Rice.

ABSTRACT: Reproductive isolation is an obstacle for plant breeding when a distant cross is demanded. It can be divided into two main types based on different growth stages: prezygotic isolation and postzygotic isolation. The hybrid weakness, which is a type of postzygotic isolation, can become a problem in crop breeding. In order to overcome reproductive isolation, it is necessary to elucidate its mechanism. In this study, genetic analysis for low temperature-dependent hybrid weakness was conducted in a rice F₂ population derived from Taichung 65 (T65, Japonica) and Lijiangxintuanheigu (LTH, Japonica). The weak and severe weak plants in F₂ showed shorter culm length, late heading, reduced panicle number, decreased grain numbers per panicle, and impaired root development in the field. Our result also showed that hybrid weakness was affected by temperature. It was observed that 24°C enhanced hybrid weakness, whereas 34°C showed recovery from hybrid weakness. In terms of the morphology of embryos, no difference was observed. Therefore, hybrid weakness affects postembryonic development and is independent of embryogenesis. The genotypes of 126 F₂ plants were determined through genotyping-by-sequencing and a linkage map consisting of 862 single nucleotide polymorphism markers was obtained. Two major quantitative trait loci (QTLs) were detected on chromosomes 1 [hybrid weakness j 1 (hwj1)] and 11 [hybrid weakness j 2 (hwj2)]. Further genotyping indicated that the hybrid weakness was due to an incompatible interaction between the T65 allele of hwj1 and the LTH allele of hwj2. A large F₂ populations consisting of 5,722 plants were used for fine mapping of hwj1 and hwj2. The two loci, hwj1 and hwj2, were mapped in regions of 65-kb on chromosome 1 and 145-kb on chromosome 11, respectively. For hwj1, the 65-kb region contained 11 predicted genes, while in the hwj2 region, 22 predicted genes were identified, two of which are disease resistance-related genes. The identified genes along these regions serve as preliminary information on the molecular networks associated with hybrid weakness in rice.

SUBMITTER: Than Kutay Soe

PROVIDER: S-EPMC9274174 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Reproductive barriers perform a vital role during speciation1. Hybrid weakness, the poor development of hybrids compared to their parents, hinders gene exchange between different species at the postzygotic stage2,3. The molecular and evolutionary mechanisms of hybrid weakness are poorly understood2. Here, we report that two incompatible dominant loci (Hwi1 and Hwi2) involving three genes determine the high temperature-dependent expression of hybrid weakness in interspecific hybrids of rice. Hwi1 comprises two indispensable wild rice (Oryza rufipogon)-specific leucine-rich repeat receptor-like kinase (LRR-RLK) genes, 25L1 and 25L2, for inducing hybrid weakness, and the genes possibly undergo balancing selection. Hwi2, a rare allele that is predominantly distributed in indica rice (Oryza sativa), encodes a secreted putative subtilisin-like protease. Functional analysis indicated that pyramiding of Hwi1 and Hwi2 activates the autoimmune response in the basal nodes of hybrids, interrupting root formation and then impairing shoot growth, likely due to immune signal is transmitted from the basal nodes to the above-ground parts. Considering the nature of RLK activity of Hwi1 and the protease activity of Hwi2, we propose that a certain endogenous signaling molecule produced by Hwi2 is perceived by Hwi1 to activate autoimmunity through ligand-receptor signal transduction. These findings bring new insights into our understanding of reproductive isolation and may benefit rice breeding to maximally utilize invaluable genes from wild rice. We conducted microarray analysis to unravel the global changes in gene expression of a pair of NILs (nearly isogenic lines). Plants were cultivated at constant 20°C for 20 days and then shifted to constant 30°C conditions. The basal nodes of NIL(Hwi1) and NIL(hwi1) were harvested immediately before the temperature shift (set as the 0 point) or at 3, 7 or 15 days after the shift. Three biological replicates (each comprising basal nodes from 15–20 individuals) were used for each time point.

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A Novel Combination of Genes Causing Temperature-Sensitive Hybrid Weakness in Rice.

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