The Photorespiration And Related Gene Expression Research In The Mutant Of Yellow Green Leaf Rice

In the process of producing hybrid rice seed, it was very hard and expensive to remove the mixed strains of sterile lines group, and it is also a technology link to affect the hybrid rice seed purity. The mutant of yellow green leaf is such an ideal leaf mutant. In previous studies of our laboratory, we found the spikelet numbers, stigma exsertion rate and flowering time of the mutant of yellow green leaf were same as that of wild-type control. There were no significant difference of the agronomic traits between the cross combination which came from the maintainers D100and R96-1and the combination from control. We also found the total photosynthetic pigment content of the mutant of yellow green leaf was about50%lower, which was the main cause of the yellow green leaf. And reveals the mutant of yellow green leaf special photosynthetic characteristics, which the photosynthetic rate of the mutant of yellow green leaf was higher than control under strong light and lower under weak light. However, there is lacking of in-depth research of the high photosynthetic efficiency physiological mechanisms of the mutant of yellow green leaf currently, and whether it related to the strength of photorespiration or not is a question which is worth exploring.In this research, we studied the difference between control and the mutant of yellow green leaf in the photorespiration rate, the activity of photorespiration related enzyme and the relative expression levels of photorespiration related genes intended to promoting the understanding of photosynthetic characteristics of the mutant of yellow green leaf, and promoting the application of the mutant. The main results are as follows:1. The comparison of photorespiration rateWhether the control or the mutant, the daily variation of photorespiration rate is with the increasing of light intensity and photosynthetic rate gradually increased, then reaches a maximum at13o’clock, and gradually reduce at last. Compared with control, the photorespiration rate of mutant is lower.2. The comparison of the activity of photorespiration related enzymeThe mutant’s basic trend of CAT and GS activity is the same as photorespiration rate’s tendency, and its activity lower than control. The activity at11:00-13:00obviously higher than other times, and reaches a maximum at13o’clock.3. The comparision of the relative expression levels of photorespiration related genesWe compared mutant with control the relative expression levels of photorespiration related genes, such as, OsGLYK、OsPGLP、OsGLO5、 OsmSHMT. The results shows they up with time, and keep relatively stable when reaches maximum, then gradually reduce at last. 4. Stomatal conductance and "Midday depression"The mutant’s stomatal conductance obviously higher than control under the normal air condition and the2%O2gas condition. And the stomatal conductance under the2%O2gas condition is obviously higher than normal air condition. In "Midday depression", the stomatal conductance of control greatly reduced, while the mutant was relatively normal.The results show that although the total photosynthetic pigment content of the mutant of yellow green leaf was about50%lower than control, its photorespiration rate lower than control, this may be one of the important reasons that the mutant has a high photosynthetic efficiency. And under the strong light condition when midday, the stomatal conductance of mutant higher than control, and additionally its photorespiration rate is lower, this may be the two main physiological reasons that contributed to the mutant had no "Midday depression" phenomenon. And there is no "Midday depression" phenomenon may be another important reason for the high photosynthetic efficiency of the mutant.Most mutants of color leaf are lethal mutation or mutations which poor growth. But the mutant of yellow green leaf can grow healthy, its special photosynthetic feature is the physiological basis to ensure normal growth. While this article makes some discussion in the photorespiration rate, but the molecular mechanisms of photorespiration need further study.