Dataset Information

A diverse set of microRNAs and microRNA-like small RNAs in developing rice grains.

ABSTRACT: Endogenous small RNAs, including microRNAs (miRNAs) and short-interfering RNAs (siRNAs), function as post-transcriptional or transcriptional regulators in plants. miRNA function is essential for normal plant development and therefore is likely to be important in the growth of the rice grain. To investigate the roles of miRNAs in rice grain development, we carried out deep sequencing of the small RNA populations of rice grains at two developmental stages. In a data set of approximately 5.5 million sequences, we found representatives of all 20 conserved plant miRNA families. We used an approach based on the presence of miRNA and miRNA* sequences to identify 39 novel, nonconserved rice miRNA families expressed in grains. Cleavage of predicted target mRNAs was confirmed for a number of the new miRNAs. We identified a putative mirtron, indicating that plants may also use spliced introns as a source of miRNAs. We also identified a miRNA-like long hairpin that generates phased 21 nt small RNAs, strongly expressed in developing grains, and show that these small RNAs act in trans to cleave target mRNAs. Comparison of the population of miRNAs and miRNA-like siRNAs in grains to those in other parts of the rice plant reveals that many are expressed in an organ-specific manner.

SUBMITTER: Zhu QH

PROVIDER: S-EPMC2527712 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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A diverse set of microRNAs and microRNA-like small RNAs in developing rice grains.

Zhu Qian-Hao QH Spriggs Andrew A Matthew Louisa L Fan Longjiang L Kennedy Gavin G Gubler Frank F Helliwell Chris C

Genome research 20080807 9

Endogenous small RNAs, including microRNAs (miRNAs) and short-interfering RNAs (siRNAs), function as post-transcriptional or transcriptional regulators in plants. miRNA function is essential for normal plant development and therefore is likely to be important in the growth of the rice grain. To investigate the roles of miRNAs in rice grain development, we carried out deep sequencing of the small RNA populations of rice grains at two developmental stages. In a data set of approximately 5.5 millio ...[more]

PMID: 18687877

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Project description:Endogenous small RNAs, including microRNAs (miRNAs) and short-interfering RNAs (siRNAs), function as posttranscriptional or transcriptional regulators in plants. miRNA function is essential for normal development and therefore likely to be important in the growth of the rice grain. To investigate the likely roles of miRNAs in rice grain development we carried out deep sequencing of the small RNA populations of rice grains. A total of 96,091 (including 23,867 reads from vegetative tissues) and 5,379,724 small RNA sequences that are longer than 17nt were generated. Approximately 94% of these small RNAs were 20-24nt in length. The majority of the small RNAs were singletons, indicating that rice genome has a very complex small RNA population, which is harder to be saturated. From these smal RNA sequences we found representatives of all 20 conserved plant miRNA families and evidence for changes in expression of miRNAs during rice grain development. Using an approach based on the presence of the miRNA and miRNA* sequences, we identified 51 novel, non-conserved rice miRNA families expressed in grains with functionally diverse predicted target genes. miRNA-guided cleavage was confirmed for a number of targets genes including ones with roles in sugar signalling and restoration of cytoplasmic male sterility. We identified a likely mirtron, indicating that plants can also use spliced introns as a source of miRNAs. Our sequencing results revealed four TAS3 loci; these all contain dual miR390 sites of which only the 3? site is cleaved. We also found a miRNA-like long hairpin generating phased 21nt small RNAs, strongly expressed in developing grains and show that these small RNAs act in trans to cleave target mRNAs. Keywords: high throughput pyrosequencing, small RNA, microRNA, grain development, rice Small RNA populations of shoots and roots of 7 days old seedlings, and 1-5 and 6-10 days after fertilization grains were determined using high throughput sequencing technology. The abundance of known miRNAs were compared based on the number of sequence reads. To give a whole picture of the rice small RNA populations and to reflect un-biasly the sequencing results, small RNAs that are longer than 17nt no matter whether or not they matched with the rice genome were included in this submitted dataset. The unmatched sequences may be derived from un-sequenced regions or sequencing errors.

Project description:High temperature impairs starch biosynthesis in developing rice grains and thereby increases chalkiness, affecting the grain quality. Genome encoded microRNAs (miRNAs) fine-tune target transcript abundances in a spatio-temporal specific manner, and this mode of gene regulation is critical for a myriad of developmental processes as well as stress responses. However, the role of miRNAs in maintaining rice grain quality/chalkiness during high daytime temperature (HDT) stress is relatively unknown. To uncover the role of miRNAs in this process, we used five contrasting rice genotypes (low chalky lines Cyp, Ben, and KB and high chalky lines LaGrue and NB) and compared the miRNA profiles in the R6 stage caryopsis samples from plants subjected to prolonged HDT (from the onset of fertilization through R6 stage of caryopsis development). Our small RNA analysis has identified approximately 744 miRNAs that can be grouped into 291 families. Of these, 186 miRNAs belonging to 103 families are differentially regulated under HDT. Only two miRNAs, Osa-miR444f and Osa-miR1866-5p, were upregulated in all genotypes, implying that the regulations greatly varied between the genotypes. Furthermore, not even a single miRNA was commonly up/down regulated specifically in the three tolerant genotypes. However, three miRNAs (Osa-miR1866-3p, Osa-miR5150-3p and canH-miR9774a,b-3p) were commonly upregulated and onemiRNA (Osa-miR393b-5p) was commonly downregulated specifically in the sensitive genotypes (LaGrue and NB). These observations suggest that few similarities exist within the low chalky or high chalky genotypes, possibly due to high genetic variation. Among the five genotypes used, Cypress and LaGrue are genetically closely related, but exhibit contrasting chalkiness under HDT, and thus, a comparison between them is most relevant. This comparison revealed a general tendency for Cypress to display miRNA regulations that could decrease chalkiness under HDT compared with LaGrue. This study suggests that miRNAs could play an important role in maintaining grain quality in HDT-stressed rice.

Project description:Global warming impairs grain filling in rice and reduces starch accumulation in the endosperm, leading to chalky-appearing grains, which damages their market value. We found previously that high temperature-induced expression of starch-lytic ?-amylases during ripening is crucial for grain chalkiness. Because the rice genome carries at least eight functional ?-amylase genes, identification of the ?-amylase(s) that contribute most strongly to the production of chalky grains could accelerate efficient breeding. To identify ?-amylase genes responsible for the production of chalky grains, we characterized the histological expression pattern of eight ?-amylase genes and the influences of their overexpression on grain appearance and carbohydrate components through a series of experiments with transgenic rice plants. The promoter activity of most ?-amylase genes was elevated to various extents at high temperature. Among them, the expression of Amy1A and Amy3C was induced in the internal, especially basal to dorsal, region of developing endosperm, whereas that of Amy3D was confined near the ventral aleurone. These regions coincided with the site of occurrence of chalkiness, which was in clear contrast to conventionally known expression patterns of the enzyme in the scutellum and aleurone during seed germination. Furthermore, overexpression of ?-amylase genes, except for Amy3E, in developing endosperm produced various degrees of chalky grains without heat exposure, whereas that of Amy3E yielded normal translucent grains, as was the case in the vector control, even though Amy3E-overexpressing grains contained enhanced ?-amylase activities. The weight of the chalky grains was decreased due to reduced amounts of starch, and microscopic observation of the chalky part of these grains revealed that their endosperm consisted of loosely packed round starch granules that had numerous pits on their surface, confirming the hydrolysis of the starch reserve by ?-amylases. Moreover, the chalky grains contained increased amounts of soluble sugars including maltooligosaccharides at the expense of starch. The integrated analyses proposed that expression of Amy1A, Amy3C, and Amy3D at the specific regions of the developing endosperm could generate the chalkiness. This finding provides the fundamental knowledge to narrow down the targets for the development of high temperature-tolerant premium rice.

Dataset Information

A diverse set of microRNAs and microRNA-like small RNAs in developing rice grains.

Publications

A diverse set of microRNAs and microRNA-like small RNAs in developing rice grains.

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