Project description:Rice in tropical and sub-tropical areas is often subjected to cold stress at the seedling stage, resulting in poor growth and yield loss. Although japonica rice is generally more cold tolerant (CT) than indica rice, there are several favorable alleles for CT exist in indica that can be used to enhance CT in rice with a japonica background. Genome-wide gene expression profiling is an efficient way to decipher the molecular genetic mechanisms of CT enhancement and to provide valuable information for CT improvement in rice molecular breeding. In this study, the transcriptome of the CT introgression line (IL) K354 and its recurrent parent C418 under cold stress were comparatively analyzed to explore the possible CT enhancement mechanisms of K354.A total of 3184 differentially expressed genes (DEGs), including 195 transcription factors, were identified in both lines under cold stress. About half of these DEGs were commonly regulated and involved in major cold responsive pathways associated with OsDREB1 and OsMyb4 regulons. K354-specific cold-induced genes were functionally related to stimulus response, cellular cell wall organization, and microtubule-based movement processes that may contribute to increase CT. A set of genes encoding membrane fluidity and defensive proteins were highly enriched only in K354, suggesting that they contribute to the inherent CT of K354. Candidate gene prediction based on introgressed regions in K354 revealed genotype-dependent CT enhancement mechanisms, associated with Sir2, OsFAD7, OsWAK112d, and programmed cell death (PCD) related genes, present in CT IL K354 but absent in its recurrent parent C418. In K354, a number of DEGs were co-localized onto introgressed segments associated with CT QTLs, providing a basis for gene cloning and elucidation of molecular mechanisms responsible for CT in rice.Genome-wide gene expression analysis revealed that genotype-specific cold induced genes and genes with higher basal expression in the CT genotype contribute jointly to CT improvement. The molecular genetic pathways of cold stress tolerance uncovered in this study, as well as the DEGs co-localized with CT-related QTLs, will serve as useful resources for further functional dissection of the molecular mechanisms of cold stress response in rice.

Project description:Rice in tropical and sub-tropical areas is often subjected to cold stress at the seedling stage resulting in poor growth and yield loss. In general, japonica rice has stronger cold tolerance (CT) than indica rice. However, several favorite alleles for CT exist in indica rice and can be used to enhance CT under japonica background. Genome-wide gene expression profiling is the efficient way to decipher the molecular genetic mechanism of CT enhancement and provide valuable information for the CT improvement in rice molecular breeding. In this study, the transcriptome of a CT introgressed line (IL) K354 and its recurrent parent C418 under cold stress were comparatively analyzed to explore the possible CT enhancement mechanism of K354.Totally 3184 differentially expressed genes (DEGs) including 195 transcription factors were identified in both lines under cold stress, about half of them were commonly regulated, which were involved in the major cold responsive pathways including OsDREB1s regulon. The K354-specific cold-induced DEGs were mainly related to stimulus response, cellular cell wall organization, and microtubule-based movement process compared with commonly cold-induced DEGs by GO analysis. Moreover, 296 constitutive DEGs with significantly different transcription level between C418 and K354 were detected under both control and cold stress conditions. K354-specific cold-regulated and constitutive DEGs jointly account for the CT improvement of K354. Pathway analysis unraveled up-regulation of starch and sucrose metabolism in both genotypes and presumably weaker defense response to stress in K354 than C418 under cold stress. Candidate genes prediction based on previous putative CT genetic networks revealed genotype-dependent CT enhancement mechanism in CT IL K354 vs recurrent parent C418, including Sir2, OsFAD7, OsWAK112d, and PCD related genes, etc.We propose a hypothesis of the CT enhancement mechanism in rice based on the results in present study. Firstly, a number of cold-regulated genes are able to express constitutively at high level or absent under control condition for standing by the arrival of cold stress. Next, under cold stress slower perception of stress signal from the more cold-tolerant membrane can postpone the activation of defensive system which may have possible negative effects on rice growth. Then, PCD will be launched to sacrifice a few cells for maintaining the basal growth of most cells. Finally, the protective responses on multiple aspects of cold damage will be postponed because of delayed several cold-defensive pathways (i.e. OsDREB1C regulon). It might explain why the recovery capacity of K354 from cold stress to control condition is stronger than C418. The CT enhancement mechanism can be regarded as the possible way to improve CT of japonica rice using indica germplasm in rice breeding program.

Project description:Rice in tropical and sub-tropical areas is often subjected to cold stress at the seedling stage resulting in poor growth and yield loss. In general, japonica rice has stronger cold tolerance (CT) than indica rice. However, several favorite alleles for CT exist in indica rice and can be used to enhance CT under japonica background. Genome-wide gene expression profiling is the efficient way to decipher the molecular genetic mechanism of CT enhancement and provide valuable information for the CT improvement in rice molecular breeding. In this study, the transcriptome of a CT introgressed line (IL) K354 and its recurrent parent C418 under cold stress were comparatively analyzed to explore the possible CT enhancement mechanism of K354.Totally 3184 differentially expressed genes (DEGs) including 195 transcription factors were identified in both lines under cold stress, about half of them were commonly regulated, which were involved in the major cold responsive pathways including OsDREB1s regulon. The K354-specific cold-induced DEGs were mainly related to stimulus response, cellular cell wall organization, and microtubule-based movement process compared with commonly cold-induced DEGs by GO analysis. Moreover, 296 constitutive DEGs with significantly different transcription level between C418 and K354 were detected under both control and cold stress conditions. K354-specific cold-regulated and constitutive DEGs jointly account for the CT improvement of K354. Pathway analysis unraveled up-regulation of starch and sucrose metabolism in both genotypes and presumably weaker defense response to stress in K354 than C418 under cold stress. Candidate genes prediction based on previous putative CT genetic networks revealed genotype-dependent CT enhancement mechanism in CT IL K354 vs recurrent parent C418, including Sir2, OsFAD7, OsWAK112d, and PCD related genes, etc.We propose a hypothesis of the CT enhancement mechanism in rice based on the results in present study. Firstly, a number of cold-regulated genes are able to express constitutively at high level or absent under control condition for standing by the arrival of cold stress. Next, under cold stress slower perception of stress signal from the more cold-tolerant membrane can postpone the activation of defensive system which may have possible negative effects on rice growth. Then, PCD will be launched to sacrifice a few cells for maintaining the basal growth of most cells. Finally, the protective responses on multiple aspects of cold damage will be postponed because of delayed several cold-defensive pathways (i.e. OsDREB1C regulon). It might explain why the recovery capacity of K354 from cold stress to control condition is stronger than C418. The CT enhancement mechanism can be regarded as the possible way to improve CT of japonica rice using indica germplasm in rice breeding program. In this study, the specific gene expression patterns of two genotypes (C418 and K354) at 2h, 6h, 12h, 24h and 48h during cold stress treatment (4 C) and control were characterized by using the Affymetrix rice microarray platform.

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A novel functional gene associated with cold tolerance at the seedling stage in rice.

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A novel functional gene associated with cold tolerance at the seedling stage in rice.

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