| Rice is one of the most important food crops in China.Most of rice quality traits are quantitative traits controlled by multiple genes,which are more complex and genetically affected by external environmental conditions.Elucidating the mechanisms of quality differences between varieties could provide theoretical guide for rice quality improvement.In this study,milling quality,appearance quality,eating and cooking quality,and RVA viscosity characteristics of 208 japonica rice germplasm were evaluated and the relevance between quality traits was discussed.Two materials,Lamujia and Shuijing 3,which were differential in many quality traits,were selected to study the mechanism of quality difference by using high-throughput transcriptome sequencing technique.Genes expression at 7 days and 14 days after flowering were analyzed and the main results were as following:1.The 208 germplasm resources had a large coefficient of variation in quality traits,with a wide range of variation and rich genetic diversity.There were significant or extremely significant correlations between chalkiness rate/the chalkiness degree and the length-width ratio,alkali spreading value and the taste value.In addition,there was significant correlation between the alkali spreading value and other quality traits.According to the Ministry of Agriculture's industry standard,"Quality of Edible Rice Variety" NY/T-593-2013,the quality evaluation of Nipponbare,Xinfeng 6 and Shuijing 3 had good performance,and Banjiemang,Huangkezaogan,Lixinjing had bad performance.2.The correlation analysis of the RVA parameters and other quality traits showed that amylose content,gel consistency,gelatinization temperature,and taste value were all significantly correlated with the RVA parameters.HPV,CPV,SBV,CSV values were significantly negatively correlated with milled rice rate and head rice rate.There was significantly negative correlation between BDV,Pe T,PKV,Pa T and chalkiness rate/chalkiness degree.Significantly negative correlation was found between Pa T and brown rice rate,significantly positive correlation between chalkiness rate and chalkiness.3.By using high-throughput transcriptome sequencing of two materials,Lamujia and Shuijing 3,it was found that a total of 3376 differentially expressed genes were found in the 7 DAF sample,including 1670up-regulated genes and 1706 down-regulated genes;and a total of 1559 differentially expressed genes were found in the 14 DAF samples,including 618 up-regulated genes and 941 down-regulated genes.The results of GO enrichment analysis showed that the biological processes of 7 DAF differentially expressed genes were mainly enriched in response to temperature stimuli,trehalose synthesis and metabolism,hormone-mediated and signal transduction pathways.The molecular functions involved in the differential genes are mainly enriched in some transcription factor activities and transcriptional regulation activities;cellular components are enriched in the nucleus.The biological processes of 14 DAF differentially expressed genes were mainly enriched in fruit and seed development,and responded to temperature stimuli;the molecular functions involved in the differential genes were enriched in xyloglucanyl transferase activity,hydrolase activity,and transcriptional regulation activity.Unlike the 7 DAF differentially expressed genes,the cell component of the 14 DAF differentially expressed genes was enriched in the plasma membrane and cell wall.The KEGG metabolic pathway analysis showed that the differentially expressed genes at 7 DAF and 14 DAF were located in 114 and 109 KEGG pathway pathways,respectively.The 7 DAF DEGs were mainly enriched in the processes of ribosome,phytohormone signal transduction,protein processing in the endoplasmic reticulum,starch and sucrose metabolism,etc.While,14 DAF of DEGs enriched in carbon metabolism,amino acid biosynthesis,phytohormone signal transduction,ribosome,etc.The differentially expressed genes enriched in these pathways might be involved in the formation of differential quality traits in Lamujia and Shuijing 3. |
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