Comparison Between QTLs for Chlorophyll Content and Genes Controlling Chlorophyll Biosynthesis and Degradation in Japonica Rice

Abstract

The objectives of this study were to understand the expression patterns of chlorophyll content-related genes at different growth stages of rice ( Oryza sativa L.) and to disclose the genetic mechanism of stay-green at later stage. Quantitative trait loci (QTLs) controlling chlorophyll content at tillering, heading, and maturity stages were located using 126 recombinant inbred lines (RILs) derived from a cross between 2 japonica rice cultivars, Shennong 265 and Lijiang Xintuanheigu. A total of 22 QTLs for chlorophyll content were identified, of which 5 loci were expressed at tillering stage, 7 at heading stage, and 10 at maturity stage. These QTLs were located on all the rice chromosomes except chromosome 5. According to the comparison between the locations of these QTLs and genes underlying the key enzymes of chlorophyll biosynthesis and degradation, relatively rich QTLs for chlorophyll biosynthesis and degradation at earlier stage were located in the regions harboring the loci for chlorophyll content. With the process of plant growth, more QTLs were detected but only a few of them were involved in chlorophyll biosynthesis and degradation. These results suggest that the expression levels of most genes/QTLs for chlorophyll biosynthesis or degradation were not different at earlier stage but the expression levels of specific key genes were increased at later stage. Therefore, the genetic basis for stay-green is proposed in 2 pathways: increase of transcripts for chlorophyll biosynthesis-related genes and decrease of expression for chlorophyll degradation genes.