LAUSR

In this study, rice cultivar 8272 (yellowing leaves) was compared with cultivar 9311 (normal leaf color) to clarify the mechanism underlying the chlorosis. The 8272 leaf color was sensitive to intense sunlight accompanied by high temperatures, which induced the yellowing of leaves, whereas the 9311 leaf color was normal under the same growing conditions. A shading experiment in the field and an artificial climate chamber test revealed that the chlorosis of 8272 leaves was due to high-intensity light, rather than high temperatures. Analyses of chlorophyll fluorescence parameters indicated that the photosystem II (PSII) reaction center activity of 8272N (grown under natural high light conditions) was significantly lower than that of 8272S (under shade), with the electron transfer significantly inhibited. The H2O2, O2.−, and malondialdehyde (MDA) contents increased sharply in 8272N, and the antioxidant enzymes were also activated. A comparison of the enriched KEGG pathways among the differentially expressed genes (DEGs) between 8272 and 9311 indicated genes related to abiotic stress tolerance were highly expressed in 8272N. In contrast, the expression levels of the key genes in the carbon assimilation metabolic pathway were significantly lower in 8272N than in 9311N. A qRT-PCR analysis confirmed the results of the RNA-seq and antioxidant enzyme activity analyses. Thus, the chlorosis of 8272 leaves in response to intense light may be associated with the mechanisms contributing to the photosynthetic control of electron transport via carbon assimilation in leaves.