Studies On Photosynthesis Physiological Characteristics,Molecular Mechanism,Carbon And Nitrogen Transport Of Yellow-green Leaf Mutant Jimai5265yg In Wheat

Leaf color mutants are not only an ideal material for studying chlorophyll synthesis,chloroplast development and photosynthesis,but also can be applied in cross breeding as marker traits.In this paper,the agronomic characters,subcellular structure,photosynthetic characteristics,carbon and nitrogen metabolism were studied in the yellow-green leaf mutants jimai5265yg and wild-type jimai5265.The concentration changes of cytochrome content and chlorophyll synthesis precursors were detected to reveal the physiological reasons of leaf color mutation.The photosynthetic index and chlorophyll fluorescence parameters were measured to analyze the changes of photosynthetic characteristics.Transcriptome sequencing was performed on yellow-green mutants and wild-type leaves to analyze the metabolic pathways that may be involved in.The effects of wheat leaf color mutation on carbon and nitrogen metabolism mechanism were studied by comparing the accumulation and distribution of dry matter and nitrogen compounds between mutants and wild-type organs.The main findings are as follows:1.The leaves of the yellow-green leaf mutant jimai 5265yg showed light yellow at germination,and the leaves changed from light yellow to yellowish green at growth and development,and continued to harvest.The leaf length,leaf width and leaf area of flag leaf,inverted second leaf and inverted third leaf of jimai5265yg were slightly lower than those of the wild type,but the leaf weight was higher than that of the wild type.The plant height,grain number and 1000-grain weight of jimai5265yg were significantly lower than those of wild type,and the panicle length and spikelet number did not change significantly.2.The analysis of pigment content showed that the chlorophylla and chlorophyllb contents of jimai5265yg were significantly reduced,which were only 61.3%and 41.9%of those of the wild type jimai5265.The chloroplasts in mesophyll cells of jima5265yg were slightly swollen and globular.The thylakoid lamellae were reduced,and the basal granule and matrix lamellae were fuzzy and loose in different degrees.The concentration and accumulation of chlorophyll biosynthesis precursor substance ALA increased,the relative fluorescence and concentration of Proto IX and Pchlide decreased,and the synthesis of proporphyrin IX to magnesium proporphyrin IX was hindered.The physiological indexes showed that the soluble protein content,soluble sugar content,activity of superoxide dismutase and activity of catalase of jimai5265yg were higher than those of wild type,but the content of malondialdehyde was lower than that of wild type.3.By transcriptome sequencing of leaves in jimai5265yg and jimai5265,259differentially expressed genes were obtained,and 58 GO terms were significantly enriched,including 116 up-regulated transcripts and 48 down-regulated transcripts.51.7%(30/58)of GO entries were related to cytochrome synthesis,chloroplast development,and photosynthesis.The KEGG pathway enrichment analysis indicated that the photosynthetic regulation antenna pathway was significant.4.Comparing the protein expression profiles of leaf in jimai5265yg and jimai5265,71differential expressed proteins(DEPs)were obtained,and their m RNA also showed similar expression patterns.GO and KEGG enrichment analysis showed that DEPs were mainly enriched in photosynthesis-antenna protein,chlorophyll metabolism as well as pigment binding,which was basically consistent with transcriptome results.Finally,118 RNA editing events were found among them and A to C editing in the 3-UTR of Traes CS6D02G401500lead to its high expression in mutant through removing the inhibition of tae-mi R9781,which might involve in regulating the production of yellow-green mutant.5.The net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of the mutant were higher than those of the wild type.PS?maximum light energy conversion efficiency(F_v/F_m')and the actual photochemical efficiency(?PS?)in the mutant were higher than in the wild type,the photochemical quenching(NPQ)is lower than the wild type.It shows that jimai5265yg has a high utilization rate and conversion of light energy.6.The dry matter accumulation of the mutant was lower than that of the wild type,but the distribution ratio of dry matter in organs and the grain harvest index did not change significantly.The contribution of transshipment volume to grains,transfer rate and transfer volume of dry matter stored before flowering in jimai5265yg was significantly higher than that in jimai5265,but the assimilation amount and contribution rate of dry matter stored after flowering were significantly lower than that in the wild type.Leaf color mutation significantly reduced the accumulation of nitrogen at flowering stage,while the difference of nitrogen accumulation was not significant at maturity stage.The nitrogen retransport efficiency of the leaves in jimai5265yg was slightly lower than that in the wild type,and the nitrogen transport rate and contribution rate of the stem to the grains were significantly lower than that in the wild type.However,the nitrogen distribution ratio and nitrogen content in the grains of the mutant were significantly higher than that in the wild type at the mature stage.7.The ¹³C fixed amount of the mutant jimai5265yg was significantly reduced,the ¹³C photosynthetic output of the leaves and stems was decreased,and the ¹³C photosynthetic input of the grains was also decreased.The photosynthetic proportion of ¹³C distribution in the leaves of jimai5265yg increased obviously,while that in the stems decreased.Jimai5265yg responded rapidly to ¹⁵N,and the ¹⁵N abundance of flag leaves and grains was significantly higher than that of jimai5265.The proportion of ¹⁵N in the leaves of jimai5265yg was higher than that of jimai5265,but the proportion of ¹⁵N in grains was lower than that of jimai5265.