- Email: [email protected]
Plant microRNAs at a glance
Seminars in Cell & Developmental Biology 21 (2010) 781
Contents lists available at ScienceDirect
Seminars in Cell & Developmental Biology journal homepage: www.elsevier.com/locate/semcdb
Editorial
Plant microRNAs at a glance
microRNAs (miRNAs) are 21–24 nucleotide (nt) RNAs present in multiple lineages in plants and animals. Mechanisms underlying the biogenesis and modes of action of miRNAs are largely conserved between plants and animals, although differences also exist. This mini review series covers a few but wide-ranging topics on plant miRNAs and provides a glimpse into the intricacies of plant miRNA metabolism and function that in some respects are similar to, but in others distinct from, those of animal miRNAs. In terms of gene structure and evolution, the topics of the article by Guiliang Tang, plant miRNA genes differ from animal miRNA genes. A large number of animal miRNA genes reside in introns of other transcriptional units, usually those of protein coding genes, and the miRNAs are processed in a splicing-independent or splicing-dependent manner (in the case of mirtrons) (reviewed in [1]). Most plant miRNA genes reside in intergenic regions and have their own transcriptional units. A study on lineage-specific (i.e. newly evolved or young) miRNAs from plants shows that plant miRNAs can arise from the inverted duplication of a target gene [2]. This was based on the extensive sequence similarity between the pre-miRNA and the target gene. To my knowledge, such a mechanism of miRNA evolution has not been documented in animals. In this series, Guiliang Tang examined the sequences of both the precursor to a miRNA conserved in many plant lineages (i.e. not newly evolved) and its target genes and revealed traces of similarities that indicate origination of the miRNA from its target gene. In terms of biogenesis, modes of action, and biological functions, plant miRNAs show similar as well as unique features as compared to animal miRNAs. In the article by Zhixin Xie, the mechanisms of miRNA biogenesis and homeostasis are described. Intriguingly, similar feedback mechanisms are employed to regulate miRNA homeostasis in both plants and animals. The major miRNA processing gene DICER-LIKE1 in plants and Dicer in animals are targeted by miR162 and let-7, respectively, to achieve feedback regulation [3–5]. Ed Allen describes the unique role of plant miRNAs in the biogenesis of another class of endogenous small RNAs known as trans-acting siRNAs, which in turn regulate their own target genes.
1084-9521/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.semcdb.2010.07.005
This unique function of plant miRNAs is attributable to the ability of plant miRNAs to guide the precise cleavage of their target mRNAs and the presence of RNA-dependent RNA polymerases to generate double-stranded RNAs from the single-stranded cleavage products. This ability of plant miRNAs to trigger the production of functional, secondary small RNAs expands the regulatory power of plant miRNAs. While plant miRNAs are best known for targeting transcription factor genes to regulate a myriad of developmental processes [6], they are also increasingly recognized as regulators of responses to the environment. The article by Ramanjulu Sunkar describes the roles of miRNAs in various stress responses. References [1] Kim VN, Han J, Siomi MC. Biogenesis of small RNAs in animals. Nat Rev Mol Cell Biol 2009;10(2):126–39. [2] Allen E, Xie Z, Gustafson AM, Sung GH, Spatafora JW, Carrington JC. Evolution of microRNA genes by inverted duplication of target gene sequences in Arabidopsis thaliana. Nat Genet 2004;36(12):1282–90. [3] Xie Z, Kasschau KD, Carrington JC. Negative feedback regulation of DicerLike1 in Arabidopsis by microRNA-guided mRNA degradation. Curr Biol 2003;13(9):784–9. [4] Forman JJ, Legesse-Miller A, Coller HA. A search for conserved sequences in coding regions reveals that the let-7 microRNA targets Dicer within its coding sequence. Proc Natl Acad Sci USA 2008;105(39):14879–84. [5] Tokumaru S, Suzuki M, Yamada H, Nagino M, Takahashi T. let-7 regulates Dicer expression and constitutes a negative feedback loop. Carcinogenesis 2008;29(11):2073–7. [6] Chen X. Small RNAs and their roles in plant development. Annu Rev Cell Dev Biol 2009;25:21–44.
Xuemei Chen ∗ Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, 900 University Ave, Riverside, CA 92521, United States ∗ Tel.:
+1 951 827 3988; fax: +1 951 827 4437. E-mail address: [email protected] Available online 29 July 2010
Contents lists available at ScienceDirect
Seminars in Cell & Developmental Biology journal homepage: www.elsevier.com/locate/semcdb
Editorial
Plant microRNAs at a glance
microRNAs (miRNAs) are 21–24 nucleotide (nt) RNAs present in multiple lineages in plants and animals. Mechanisms underlying the biogenesis and modes of action of miRNAs are largely conserved between plants and animals, although differences also exist. This mini review series covers a few but wide-ranging topics on plant miRNAs and provides a glimpse into the intricacies of plant miRNA metabolism and function that in some respects are similar to, but in others distinct from, those of animal miRNAs. In terms of gene structure and evolution, the topics of the article by Guiliang Tang, plant miRNA genes differ from animal miRNA genes. A large number of animal miRNA genes reside in introns of other transcriptional units, usually those of protein coding genes, and the miRNAs are processed in a splicing-independent or splicing-dependent manner (in the case of mirtrons) (reviewed in [1]). Most plant miRNA genes reside in intergenic regions and have their own transcriptional units. A study on lineage-specific (i.e. newly evolved or young) miRNAs from plants shows that plant miRNAs can arise from the inverted duplication of a target gene [2]. This was based on the extensive sequence similarity between the pre-miRNA and the target gene. To my knowledge, such a mechanism of miRNA evolution has not been documented in animals. In this series, Guiliang Tang examined the sequences of both the precursor to a miRNA conserved in many plant lineages (i.e. not newly evolved) and its target genes and revealed traces of similarities that indicate origination of the miRNA from its target gene. In terms of biogenesis, modes of action, and biological functions, plant miRNAs show similar as well as unique features as compared to animal miRNAs. In the article by Zhixin Xie, the mechanisms of miRNA biogenesis and homeostasis are described. Intriguingly, similar feedback mechanisms are employed to regulate miRNA homeostasis in both plants and animals. The major miRNA processing gene DICER-LIKE1 in plants and Dicer in animals are targeted by miR162 and let-7, respectively, to achieve feedback regulation [3–5]. Ed Allen describes the unique role of plant miRNAs in the biogenesis of another class of endogenous small RNAs known as trans-acting siRNAs, which in turn regulate their own target genes.
1084-9521/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.semcdb.2010.07.005
This unique function of plant miRNAs is attributable to the ability of plant miRNAs to guide the precise cleavage of their target mRNAs and the presence of RNA-dependent RNA polymerases to generate double-stranded RNAs from the single-stranded cleavage products. This ability of plant miRNAs to trigger the production of functional, secondary small RNAs expands the regulatory power of plant miRNAs. While plant miRNAs are best known for targeting transcription factor genes to regulate a myriad of developmental processes [6], they are also increasingly recognized as regulators of responses to the environment. The article by Ramanjulu Sunkar describes the roles of miRNAs in various stress responses. References [1] Kim VN, Han J, Siomi MC. Biogenesis of small RNAs in animals. Nat Rev Mol Cell Biol 2009;10(2):126–39. [2] Allen E, Xie Z, Gustafson AM, Sung GH, Spatafora JW, Carrington JC. Evolution of microRNA genes by inverted duplication of target gene sequences in Arabidopsis thaliana. Nat Genet 2004;36(12):1282–90. [3] Xie Z, Kasschau KD, Carrington JC. Negative feedback regulation of DicerLike1 in Arabidopsis by microRNA-guided mRNA degradation. Curr Biol 2003;13(9):784–9. [4] Forman JJ, Legesse-Miller A, Coller HA. A search for conserved sequences in coding regions reveals that the let-7 microRNA targets Dicer within its coding sequence. Proc Natl Acad Sci USA 2008;105(39):14879–84. [5] Tokumaru S, Suzuki M, Yamada H, Nagino M, Takahashi T. let-7 regulates Dicer expression and constitutes a negative feedback loop. Carcinogenesis 2008;29(11):2073–7. [6] Chen X. Small RNAs and their roles in plant development. Annu Rev Cell Dev Biol 2009;25:21–44.
Xuemei Chen ∗ Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, 900 University Ave, Riverside, CA 92521, United States ∗ Tel.:
+1 951 827 3988; fax: +1 951 827 4437. E-mail address: [email protected] Available online 29 July 2010