Characterization Of Two Leaf Colour Mutants In Rice

Leaf colour mutant is an useful resource for rice genomics research. In this study, we found two leaf colour mutants at a background of japonica variety Nipponbare in our rice laboratory, White- stripe leaf mutant st10 and yellow green mutant ygl6. We conducted morphological identification, genetic analysis, determination of chlorophyll content and chlorophyll fluorescence parameters, and electron microscopy observing of chloroplast development with the two mutants. The results are summarized as follows:1. We found a temperature-sensitive white-stripe leaf mutant st10 at background of Nipponbare which is induced by ethyl methane sulphonate (Ethylmethane sulphonate, EMS). It appears white-stripe at 2-leaf or 3-leaf stage. The white-stripe becomes narrow and veins show white at early panicle formation and heading stage. The leaf colour is affected by temperature. When grown at higher temperature, it displayed white-stripe obviously, even white with grain. However, the white-stripe is narrow and the grain is normal at lower temperature. st10 is shorter than Nipponbare, but the tillering is not significant different with it. The result of genetic analysis revealed that white-stripe phenotype was controlled by a single recessive nucleic gene. The F₂ population is generated from a across between peiai64s (a male sterility line) and st10. ST10 gene was mapped in 150 kb region between marker STR19 and marker STR24 on chromosome 3. We tested the chlorophyll contents of three temperatures, 24℃, 28℃and 32℃. Chlorophyll b and chlorophyll a are significantly reduced at 32℃, however, they are did not change significantly at 24℃and 28℃. Chlorophyll Fluorescence data show that photosynthetic capacity of the mutant is lower than wild-type.2. A new leaf colour mutant ygl6 (yellow green leaf) at background of Nipponbare is founded in T-DNA insertion mutant populations of rice. This mutant shows yellow green leaf during the whole growth stage. Compared with Nipponbare, it is unsensitive to temperature, shorter, less tillers and growth period delayed. The F₂ population is generated from a across between1892s (a male sterility line) and ygl6. Genetic analysis revealed that yellow green phenotype was controlled by a single recessive nucleic gene. Finally, with the method of based cloning, YGL6 gene was mapped in 89 kb region between marker HE10 and HE20 on chromosome10. The left and right respectively have 4 and 2 exchange plants. Compared with wild-type, the analysis of chlorophyll content indicates that chlorophyla decrease by 36%, chlorophylb decrease by 94% and carotenoid decrease by 20%. Chlorophyll Fluorescence data shows that there are no significant differences between mutant and wild-type. The result of electron microscopy explains that the lamellar structure of chloroplast thylakoid is clearly decreasing.