The Leaf-etiolation Mechanism Study Of A Etiolation Foxtail Millet Mutant Siyl1

Foxtail millet is the main cereal crop in China,which is rich in nutrients needed by human and loved by people.In this study,the etiolation mutant siyl1 was selected as the experimental materials,which obtained from EMS mutagenesis of Jingu 21,a high-quality of Shanxi variety.The siyl1 mutant was studied in agronomic traits,pigment content,photosynthetic characteristics and chloroplast ultrastructure.Further study of etiolation mechanism at molecular level was carried by transcriptome sequencing.The main results are as follows:1.Compared with the wild type,the etiolation mutant siyl1 had a shorter plant height and leaf length,and a etiolation-green phenotype at seedling stage.The content of photosynthetic pigments(chlorophyll a,chlorophyll b,and carotenoids)were significantly reduced in leaves.The photosynthetic capacity,absorption and utilization of CO2 were slowed.The transpiration rate,stomatal conductance,and water use efficiency were significantly reduced.2.Observation of the ultrastructure of leaf chloroplasts at seedling stage revealed that the chloroplasts of siyl1 was mutated,such as the number of chloroplasts was reduced and the overall structure of chloroplasts was incomplete.The membrane structure was blurred and most chloroplasts were clustered at one end of the cell.The inner grain of chloroplast is sparse and scattered.There were a few chloroplast grain and some of them were self-dissoluted.3.From screening of transcriptome sequencing results in mutant siyl1 and wild-type seedling,14chlorophyll-related genes were found.The result showed that Seita.5G461800 and Seita.6G208100 genes were related to chlorophyll anabolic pathways,Seita.2G134400 gene was related to chlorophyll degradation metabolism;and Seita.9G118300 gene was related to nitrogen metabolism which was relevant to chlorophyll content in foxtail millet.4.The expression patterns of 14 genes in mutant siyl1 and wild-type were analyzed by real-time quantitative PCR.The results were consistent with transcriptome results and transcriptome sequencing data was highly correlated with fluorescent quantitative expression results.In conclusion: etiolation mutant siyl1 with lower plant height and chlorophyll content,slowed photosynthesis and abnormal thylakoid structure.Transcriptome data was consistent with real-time quantitative PCR results.The results show that the abnormal expression of chlorophyll and chloroplast-related genes may was the reason of yellowing leaves in foxtail millet..