Identification And Genetic Analysis Of Setaria Viridis Mutants(College Of Life Science, Shandong Normal University, Jinan)

With the increasing of population, people need more food and crop production needs significant increase. C_ompared with C₃ plants, C₄ plants have more energy conversion efficiency, higher use efficiency of water and nitrogen. Significant increase in crop yield will occur only if C₃ crops possess the capacity of C₄ photosynthetic, which may bring a second green revolution in agricultural production.But so far, little is known about the mechanisms of C₄ genetic regulation because C₄ photosynthesis mutants screening and analysis are relatively difficult. In this study, we adopted a new C₄ photosynthetic model species Setaria viridis, which has the many advantages, such as small plant?10-15 cm?, simple growing demand, a short life cycle, prolific seed production and so on. Mutants pool had been built by gamma ray and several possible C₄ defect mutants were obtained by screening the M2 generation group under low CO₂ condition. My work is to identify these potential C₄ mutants and construct the genetic hybrid population.In the experiment, the seeds of the 668 M2 lines were planted under normal conditions to identify the mutants that still exhibited photosynthesis-related phenotype.During the periods from the beginning of M3 generation seed sowing to final seed collection in the greenhouse, we observed the mutants phenotype, mainly including the leaf shape, leaf color, plant height, ear vein, etc. Eventually we found 10 mutants under normal greenhouse conditions whose phenotype still existed and associated with photosynthesis. Among them, 5 mutants were homozygous with stable and nondisjunction phenotypes including whole-plant yellow, leaf margin curl, dwarf,multiple tillers and so on.In order to verify whether the homozygous strains lost C₄ characters,these mutants were cultured in the super high CO₂ concentration?10000 ppm?.Unfortunately, we did not find any phenotype-rescued mutants,but the result was not enough to certify whether these mutants had relationships with C₄ photosynthesis.Using crossing method combined with phenotypic analysis we identified the genetic law of the mutants. The hybrid experiment was performed between the Setaria italica?yugu1? and the S.viridis mutants. The male parent was S.viridis mutants and the female parent was yugu1.Due to the work of crosses was relatively difficult, the finalhybrid success rate was relatively low. In this experiment, we identified two possible F1 hybrid strains. These two strains of F1 hybrids had more tillers, which was same as its male parent MC_A0860-1?13?.The tiller number was about 10, and each had a spike, which was the characteristic of yugu1 having not?wild type yugu1 only has one tiller and one spike?. Then we verified the hybrid F1 through PC_R, and the result showed that the PC_R product was different from S.viridis and S.italica. The seeds of F2 were harvested for further research.S. italica is a typical C₄ plant, which has a close relationship with S. viridis, and its genome has already been sequenced. In the first part of this project,we identified the S. viridis mutants under the condition of super high CO₂, however, we did not find any phenotype-rescued mutants, while the C₄ plant S.italica showed dwarf phenotype under the super-elevated CO₂ concentration?10000 ppm?. So the third leaf of S.italica under two conditions were collected, and RNA were extracted for transcriptome analysis. The results showed that the differentially expressed genes were enriched in carbohydrate metabolic process, oxidation-reduction process, stress response and so on. This result may help us to interpret the mechanism of C₄ plant responses to super high CO₂.