3.3 Expression rhythms of circadian clock components is altered in the oslhy mutant
As a circadian clock gene, the expression rhythm of OsLHY was examined in the oslhy mutant and WT under both LD and SD conditions. The OsLHY gene remained obvious rhythmic expression in the oslhy mutant just like that in WT, which peaked at dawn (ZT0) and reached its trough around dusk (ZT12) under both LD and SD conditions (Figure 3A and 3B). While it was reduced on the daytime and increased on the nighttime in the oslhy mutant when compared to WT (Figure 3A and 3B). The other seven circadian clock genes (OsPRR1 , OsPRR37 , OsPRR73 , OsPRR59 ,OsPRR95 , OsGI and OsELF3 ) also kept clear rhythmic expression in the oslhy mutant and WT under both LD and SD conditions, but the expression was severely influenced and the peak time of these genes was almost shifted earlier under both LD and SD conditions (Figure 3).OsPRR73and OsPRR37 were strongly repressed throughout the daytime in theoslhy mutant under LD conditions (Figure 3C and 3E), but significantly increased in the morning (ZT0 and ZT4) under SD conditions (Figure 3D and 3F). OsPRR95 and OsPRR59 were also significantly increased in the morning (ZT0 and ZT4) in the oslhy mutant under both LD and SD conditions (Figure 3G-3J). The expression of OsPRR1 and OsGI were significantly increased in the early points of daytime in theoslhy mutant (ZT4 and ZT8 under LD conditions, ZT4 forOsPRR1 and ZT0, ZT4 and ZT8 for OsGI under SD conditions) (Figure 3K-3N). In the oslhy mutant, the transcription ofOsELF3 was significantly higher than that of WT at the beginning of the day under LD conditions, while OsELF3 was significantly down-regulated from ZT8 to ZT20. Under SD conditions, the transcription of OsELF3 was increased at ZT0 and ZT12 (Figure 3O and 3P). Additionally, in the oslhy mutant, the expression peaks ofOsPRR73 , OsPRR37 , OsPRR59 , OsPRR95 were advanced by approximately 4 h or 8 h, leading to their expression peak time at ZT4 under both LD and SD conditions (Figure 3C-J). Under LD condition, the peak time of OsPRR1 and OsGI shifted approximately 4 h early and peaked at ZT8 in the oslhy mutant (Figure 3K and 3M). Under SD condition, the peak time of OsPRR1was not changed and also peaked at ZT8 in the oslhy mutant (Figure 3L). Yet the peak time of OsGI was advanced by approximately 4 h and peaked at ZT4 in the oslhy mutant (Figure 3N). These expression peak time shifts were consistent with circadian clock genes highly expressed at early daytime (Figure 3). Taken together, these results indicated that the core circadian clock geneOsLHY regulated the rhythmic expression of all tested circadian clock genes under both LD and SD conditions.