| Ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) is a pivotal enzyme in plant photosynthesis, but its activity of carboxylation in vivo is very low. The activity of Rubisco is regulated by Rubisco activase (Rubisco activase RCA). RCA plays an important role in plant light energy utilization and production, it has become a potential targets in high yield breeding. It is important in theoretical significance and application value to study the genetic basis of RCA gene expression to parse the genetic basis of photosynthesis and crop yield, and breed high-yielding varieties.We early cloned two RCA genes, ZmRCAα and ZmRCAβ. Their expression levels and maize yield in filling stage was significantly positively related in 123 maize inbred lines, and the correlation coefficient between ZmRCAβ and grain yield was higher than ZmRCAα and the three C4 genes. In the present study,242 corn recombinant inbred line (RIL) derived from a cross between RA and M53 were used as materials, we measured the expression level of ZmRCAβ in filling stage and grain yield during two consecutive years, combined with the RIL population 916 marker information to make linkage analysis; Then the expression level of ZmRCAβ in filling stage and grain yield were measured in 235 inbred lines, genome wide association analysis were proceeded combined with 558,629 SNP information, locating the QTL for yield and the eQTL regulating the expression of ZmRCAβ; Finally, the optimal promoter was detected in the 235 inbred lines.The main findings were as follows:1. Linkage analysis detected five eQTLs controlling gene expression level and four yield QTLs (LOD>2.5), five eQTLs were located on chromosome 2 and 4, respectively, namely qRCA2.1, qRCA4.1, qRCA4.2, qRCA4.3 and qRCA4.4. The percentage of variation explained by these eQTLs ranged from 5.31% to 7.5%, and with LOD scores from 3.11 to 4.96. Among them, qRCA4.2, qRCA4.3 and qRCA4.4 were detected in two years, and the qRCA4.2 was a cis-eQTL for ZmRCAβ, the remaining eQTLs were trans-eQTLs. Four QTLs were located on chromosome 1.8 and 9, respectively, namely qSY1.1, qSY1.2, qSY8.1 and qSY9.1, the percentage of variation explained by these eQTLs ranged from 4.68% to 5.69%, and with LOD scores from 2.68 to 3.23.2. Genome wide association analysis detected nine eQTLs and two yield QTLs (-logP>4.54), located in chromosome 2,4,5,8 and 10, respectively, named qNRCA2.1, qNRCA2.2, qNRCA2.3, qNRCA4.1, qNRCA4.2, qNRCA5.1, qNRCA5.2 qNRCA8.1 and qNRCA10.1. The-logP scores were from 4.54 to 5.73. And the qNRCA4.1 was the cis-eQTL for ZmRCAβ, with the remaining eQTL tran-eQTL; Two yield QTLs were located on chromosome 5, namely qNSY5.1 and qNSY5.2, and the-logP was 4.54.3. The promoter analysis was conducted the candidate genes correlation analysis with the sequences and the expression level of 235 inbred lines. Three polymorphic loci were associated with the expression level of ZmRCAβ significantly. Based on these three loci, the promoter were divided into four types, namely Type1, Type2, Type3 and Type4, and the inbred lines with Type4 promoter had the higher expression level of ZmRCAβ, Type4 promoter is the optimal promoter of ZmRCAβ in this natural population. |
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