Genetic Effects Of Heading Date Genes On Photosynthetic Traits In Rice

Both the heading date(HD)and photosynthesis are potential factors affecting rice yield,and there is a certain relationship between them in controlling rice growth and development as well as flowering and reproduction.The yield controlled by HD may be closely related to photosynthesis pathways.Both Hd1 and Ghd7 are pleiotropic genes that control heading date and yield,but their mechanism has not been clearly studied.In this study,two recombinant inbred lines,Z43 population and Z44 population constructed from Zhenshan 97/Mianyang 46,were used for the regulation of photosynthesis traits by Hd1 and Ghd7 during heading of rice under the natural long-day conditions.ZS97 carries functional Hd1 and non-functional ghd7,whereas MY46 carries non-function hd1 and functional Ghd7.The main results were summarized as follow:Hd1 and Phy B were segreated in Z43 NIL population.The main effect of Hd1 on photosynthesis-related traits was detected.Functional Hd1 decreased net photosynthetic rate,stomatal conductance,intercellular CO2 concentration,transpiration rate and total protein content,respectively;whereas increased chlorophyll content,CAT content and SOD content,respectively,during HD.However,significant effects of Phy B on photosynthetic traits,chlorophyll content and other related physiological traits were not observed.Hd1 and Ghd7 were segreated in Z44 NIL population.The main effect of Ghd7 on photosynthetic traits was detected.Functional Ghd7 reduced photosynthetic rate,stomatal conductance,intercellular CO2 concentration and transpiration rate during heading date;the effect of Hd1 on four photosynthetic traits was not detected.Meanwhile,the interaction between Hd1 and Ghd7 on photosynthetic traits were observed,functional of Hd1 required the functional Ghd7 to reduce the photosynthetic capacity during heading.In addition,the main effects of Hd1 and Ghd7 on chlorophyll content were detected,but there was no interaction between them,indicating that functional Hd1 could increase chlorophyll content,and functional Ghd7 could decrease chlorophyll content.Transcriptome analysis of two sets of near-isogenic lines revealed that Hd1 and Ghd7 do have important regulatory effects on photosynthesis and chlorophyll content.In the functional Hd1 background,functional Ghd7 caused 2836 differentially expressed genes,and 1916 down-regulated genes.In the non-functional hd1 background,functional Ghd7 caused 1097 differentially expressed genes and 621 down-regulated genes.GO function and cluster analysis showed that functional Ghd7 could significantly enrich for GO terms associated with photosynthesis and chloroplast development.Functional Ghd7 down-regulated most of the chlorophyll synthesis-related genes.However,in the functional Hd1 background,the number of genes down-regulated by functional Ghd7 was much larger than that in the non-functional hd1 background.These indicated that Ghd7 had a negative regulatory effect on chlorophyll synthesis,and its regulatory effect was stronger than when in the functional Hd1 background.In the functional Ghd7 background,functional Hd1 caused 2082 differentially expressed genes,and 1346 down-regulated genes.In the non-functional ghd7 background,Hd1 caused 564 differentially expressed genes and 262 down-regulated genes.GO function and cluster analysis showed that in the functional Ghd7 background,functional Hd1 could significantly enrich GO terms associated with photosynthesis and chloroplast development.Functional Hd1 down-regulated most of the chlorophyll synthesis-related genes,however,in the non-functional ghd7 background,functional Hd1 only significantly enriched 4 related GO terms,resulting in far fewer differentially expressed genes than when Ghd7 was functional.It was suggested that the regulation of photosynthesis by functional Hd1 is dependent on functional Ghd7.