Diural Fluctutation of Rubisco Activase Expression in Rice Leaves
ZHANG Feng JIANG De-An WENG Xiao-Yan ANG Ni-Yan (College of Life Science, Zhejiang University,Hangzhou 310029)
In order to illuminate the regulation of Rubisco activase (RCA) expression,we investigated the changes of rca mRNA accumulation in leaves of rice seedlings grown under 12-h light/12-h darkness(LD), constant darkness(DD) and constant light(LL) by Northern blotting analysis(Fig.1).The changes in RCA contents in leaves of rice seedlings grown under these three treated contidions were also studied (Fig.2) with single radial immune diffusion by rabbit polyclonal antibodies against rice Rubisco activase. Our results showed that the accumulation of rca mRNA displayed a typical oscillating pattern under LD treatment (Fig.1A),in which the levels of the maximum and minimum were detected at 8:00 a.m. and 8:00 p.m. respectively.The rhythmic accumulation pattern of rca mRNA level continued through two cycles after being transferred to DD and LL(Fig.1B,C).Under the LL treatments the peak of rca mRNA accumulation started earlier and the amplitude of the fluctuation for the second cycle was greatly reduced to approximately 20% under both DD and LL treatments. The obvious diurnal changes of RCA protein contents from the minimum levels before dawn to the maximum level in the afternoon had been observed under LD treatment (Fig.2A).It was different from that of DD and LL treatments under which it decreased gradually from the beginning to the end(Fig.2B,C).In this respect,accumulation of RCA didn't follow a circadian oscillating pattern, indicating that the transcription of RCA was regulated by an oscillating circadian rhythm and also by light but the translation of RCA was regulated by light to a large extent.