| Budget Amount *help |
¥3,780,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥480,000)
Fiscal Year 2007: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
To elucidate the repression mechanism of expression of the rice SINE, p-SINE1, we detected p-SINE1 siRNA by northern analysis using low-molecular-weight RNA purified from transgenic rice cell lines in which expression of each of five rice DCL genes (DCL1 - DCL5) were suppressed. We found that the p-SINE1 siRNA level was reduced in all of the suppression lines, especially in DCL3 and DCL5 suppression lines. This suggests that several DCL proteins, especially DCL3 and DCL5, are involved in production of p-SINE1 siRNA. We then detected p-SINE1 transcripts by northern analysis using total RNA purified from the same cell lines. We found that the p-SINE1 expression level significantly increased in DCL3 and DCL5 suppression lines. These strongly suggest that p-SINE1 siRNA is involved in repression of the p-SINE1 expression. We then examined DNA methylation of p-SINE1 sequences in these cell lines, but could not find correlation between decrease of DNA methylation level of p-SINE1 members and increase of the p-SINE1 expression level. This suggests that the mechanism other than DNA methylation is involved in repression of the p-SINE1 expression.
We also identified three new rice SINEs, OsSN1-OsSN3, which are different from p-SINE1. These had poly (A) sequences at the 3'ends, unlike p-SINE1, and showed no homology to p-SINE1. They, however, preferentially exist in gene-rich regions of chromosomes, like p-SINE1. We found that more than 20% of OsSN3 exist in introns. This suggests that siRNA generated from these SINEs possibly affects expression of genes nearby.
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