| Wheat is one of the important food crops in the world,and its yield directly affects food security.The agronomic traits of leaf color and plant height directly affect the growth and development of wheat and affect grain yield.Leaf color mutants are important materials for studying chloroplast development,chlorophyll biosynthesis,and other aspects.The discovery of the wheat returning to white line provides a material basis for the study of chlorophyll biosynthesis and plastid development in wheat leaves,and its mechanism in the process of returning to white and returning to green needs to be further studied.Plant dwarfing mutants have been widely studied and applied for their resistance to lodging and high photosynthetic efficiency.DW-B is a wheat mutant with both whitening and dwarfing characteristics.Through field agronomic traits investigation,transcriptome sequencing analysis,differential expression gene analysis,uroporphyrinogenⅢsynthase（UROS）activity assay,gibberellin sensitivity assay,chlorophyll content assay and chlorophyll fluorescence content assay of DW-B and its control parents IBG-111 and Lango,Study the physiological,biochemical,and molecular mechanisms regulating wheat dwarfing and whitening.The research results are as follows:1.This study observed the traits of the DW-B mutant and found that during the winter low temperature period,the DW-B was affected by low temperature,resulting in leaf whitening.As the temperature gradually increased the following year,the leaves returned to green.The plant height,ear height,top three nodes,bottom two nodes,and internode length under the ear of the DW-B mutant were significantly lower than their parent IBG-111.2.RNA seq was used to detect 7469 differentially expressed genes（DEGs）,of which 3920were upregulated and 3549 were downregulated,respectively.Through KEGG enrichment analysis,it was found that the chlorophyll biosynthesis pathway（porphyrin and chlorophyll metabolism pathway）was significantly enriched.The expression levels of hydroxymethylsilane synthase（Hem C）,uroporphyrinogen III synthase（Hem D,UROS）,and protochlorophyllate oxidoreductase（POR）related to porphyrin and chlorophyll synthesis were significantly upregulated in DW-B and Lango,but the enzyme activity of UROS was significantly reduced.The inhibition of chlorophyll biosynthesis in DW-B leaves is caused by a decrease in the function of the UROS protein encoded by the Hem D gene.3.The gibberellin response test found that DW-B and Lango were not sensitive to gibberellin,while IBG-111 was sensitive to gibberellin,indicating that the gibberellin signaling pathway in DW-B and Lango was inhibited.KEGG enrichment analysis in RNA Seq results showed that the expression level of GID1 related genes was significantly downregulated while the expression level of DELLA protein related genes was significantly upregulated,indicating that the downregulation of GID1 related genes in the gibberellin signaling pathway and the upregulation of DELLA related genes in DW-B led to dwarfing of DW-B.4.During the whitening period of DW-B,compared to IBG-111,the chlorophyll b（Chlb）value,carotenoids（Caro）,and total chlorophyll content（Ct）of DW-B showed a significant decrease,while the chlorophyll a（Chla）value showed no significant difference,indicating that the decrease in Chlb content was greater than the decrease in Chla,indicating that Chlb biosynthesis in DW-B was more severely damaged.This indicates a significant decrease in Chlb and Caro contents and total chlorophyll content（Ct）,leading to abnormal leaf color in DW-B.Compared with IBG-111,the maximum photosynthetic saturation potential and photosynthetic rate of DW-B were significantly reduced,which may be due to the decreased expression of photosynthetic related genes affecting light energy absorption and transformation,CO2 absorption and assimilation,and then inhibiting the Photosynthetic efficiency of DW-B plants,leading to the decline of DW-B photosynthetic rate and photosynthetic potential,and the reduction of photosynthetic pigment accumulation,leading to DW-B whitening.In this study,the DW-B mutant and its parents IBG-111 and Lango were used as materials.Through the analysis of major agronomic traits,transcriptome sequencing analysis,physiological and biochemical level analysis and pigment level analysis,the changes in gene expression and physiological and biochemical mechanisms during DW-B whitening and dwarfing were revealed,and the reasons affecting DW-B whitening and dwarfing were further clarified.These results can provide theoretical reference for molecular breeding of wheat. |
