The Effect Of PRRs Genes On Signal Transduction Of Red Light And Blue Light In Arabidopsis Thaliana

As one of the most important environmental factor,the light affects the plant development through light intensity, quantity, quality, phototropic and photoperiod. The light signal enters the circadian clock by the light receptor and brings plants physiological and biochemical activities through making the central oscillator producing oscillating and changing the output signals. Thus, the light can regulate the plant growing from the seeds germinating period to flowering period. In recent years, the light signals researches are widely carried out, but the complete light signal transduction pathway still not clearly illustrated as the light signal transduction network is very complex. PRRs (pseudo-response regulators) genes (PRR7, PRR9, TOC1) are main members of the central oscillator and they may be involved in the light signal transduction. Exploration of the role of PRRs in light signal transduction is important for detecting the light signal transduction.To determine the PRRs roles in signal transduction under different light quality, Arabidopsis prrs (prr5, prr7, prr9, toc1) null mutants and the wild type were used and the plant hypocotyls length changes under red light and blue light were observed. Then corresponding expressions rhythm of light signal transduction pathways associated genes ZTL (ZEITLUPE) and CO (CONSTANS) were analyzed by real-time quantitative PCR. At last, numbers of rosette leaves and the days of flowering for prrs mutants under long days were observed. The main results were as follows:(1) The growth hypocotyls phenotype of prrs mutants response to different lights were identified. Compared with the wide type, the hypocotyls length of the prrs mutants significantly increased under red light, while under blue light the hypocotyls length of prrs mutants shortened. But under white light and in dark, the hypocotyls length difference between the prrs mutants and the wild type were not significant. These results indicated that the PRRs may regulate plants growing by participating the light signal transduction pathway, and different PRRs genes may play different roles in different light signal transduction.(2) The ZTL and CO genes which are involved in the light signal transduction and associated with PRRs were evaluated by real-time quantitative PCR. The expression rhythm of ZTL mRNA and CO mRNA in prrs mutants were distinct from wild type under red light and blue light. The expression level of ZTL was apparently reduced and the rhythm was virtually abolished in prr5, prr7 under red light as well as in prr5, toc1 under blue light. The expression of CO was arrhythmic in prr7, prr9 under red light and in prr5 under blue light. So we presumed that the PRRs-ZTL interaction may play a role under the red light and blue light signal transduction pathway and PRRs participate in the modulation of red light and blue light on CO expression.(3) The flowering phenotypes of prrs mutants, including the number of rosette leaves and the days of flowering were detected under long days. Compared with the wide type, a late flowering phenotype was found in prrs mutants. And the numbers of rosette leaves of the prrs mutants were correspondingly more than the wild type. The result indicated that loss of PRRs genes affect the plant flowering, and this late flowering phenotype may be owing to the affection of the loss of PRRs genes on the CO gene expression.