[Show abstract][Hide abstract] ABSTRACT: Small non-coding RNAs play important roles in regulating cell functions by controlling mRNA turnover and translational repression in eukaryotic cells. Here we isolated 162 endogenous small RNA molecules from Oryza sativa, which ranged from 16 to 35 nt in length. Further analysis indicated that they represented a diversity of small RNA molecules, including 17 microRNAs (miRNAs), 30 tiny non-coding RNAs (tncRNAs) and 20 repeat-associated small interfering RNAs (rasiRNAs). Among 17 miRNAs, 13 were novel miRNA candidates and their potential targets were important regulatory genes in the rice genome. We also found that a cluster of small RNAs, including many rasiRNAs, matched to a nuclear DNA fragment that evolutionarily derived from chloroplast. These results demonstrate clearly the existence of distinct types of small RNAs in rice and further suggest that small RNAs may control gene regulation through diverse mechanisms.
[Show abstract][Hide abstract] ABSTRACT: A novel calmodulin (CaM)-binding protein of rice (Oryza sativa pollen CaM-binding protein, OsPCBP) was isolated. It contains six tetratrcopeptide repeats (TPRs) with a molecular mass of similar to 76.7 kDa. Database searches show that OsPCBP is conserved in monocots and dicots. The results from CaM-agarose pull-down assays show that OsPCBP binds to CaM in a Ca2+-dependent manner and its CaM-binding domain (CBD) is located in a segment VSKGWRLLALVLSAQQRY. Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) analysis have demonstrated that OsPCBP is a pollen-specific and late-expressed gene. Immunolocalisation showed that OsPCBP was localised in the amyloplast and intine during the late stage of pollen development. However, upon pollen hydration, there was some leakage of protein and the distribution of OsPCBP in the intine varied with the duration of hydration. After pollen germination, much OsPCBP was observed in the pollen tube wall. These results indicate the relationship of OsPCBP with starch accumulation and its involvement in pollen germination.