A genome-wide characterization of microRNA genes in maize

• Published in: PLoS genetics Vol. 5; no. 11; p. e1000716
• Main Authors: Zhang, Lifang, Chia, Jer-Ming, Kumari, Sunita, Stein, Joshua C, Liu, Zhijie, Narechania, Apurva, Maher, Christopher A, Guill, Katherine, McMullen, Michael D, Ware, Doreen
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-11-2009; Public Library of Science (PLoS)
• Subjects: Base Sequence; Computational Biology/Comparative Sequence Analysis; Conserved Sequence; Corn; Evolution; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Genetic aspects; Genetic Variation; Genetics; Genetics and Genomics/Genomics; Genetics and Genomics/Plant Genetics and Gene Expression; Genomes; Genomics; MicroRNAs - genetics; Molecular Sequence Data; Multiculturalism & pluralism; Multigene Family; Nucleotides - genetics; Ontology; Open Reading Frames - genetics; Organ Specificity - genetics; Phase transitions; Physiological aspects; Plant Biology/Plant Genetics and Gene Expression; Plant growth; Proteins; RNA; RNA Splicing - genetics; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Homology, Nucleic Acid; Sorghum; Sorghum - genetics; Structure; Synteny - genetics; Zea mays; Zea mays - genetics
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1000716

MicroRNAs (miRNAs) are small, non-coding RNAs that play essential roles in plant growth, development, and stress response. We conducted a genome-wide survey of maize miRNA genes, characterizing their structure, expression, and evolution. Computational approaches based on homology and secondary structure modeling identified 150 high-confidence genes within 26 miRNA families. For 25 families, expression was verified by deep-sequencing of small RNA libraries that were prepared from an assortment of maize tissues. PCR-RACE amplification of 68 miRNA transcript precursors, representing 18 families conserved across several plant species, showed that splice variation and the use of alternative transcriptional start and stop sites is common within this class of genes. Comparison of sequence variation data from diverse maize inbred lines versus teosinte accessions suggest that the mature miRNAs are under strong purifying selection while the flanking sequences evolve equivalently to other genes. Since maize is derived from an ancient tetraploid, the effect of whole-genome duplication on miRNA evolution was examined. We found that, like protein-coding genes, duplicated miRNA genes underwent extensive gene-loss, with approximately 35% of ancestral sites retained as duplicate homoeologous miRNA genes. This number is higher than that observed with protein-coding genes. A search for putative miRNA targets indicated bias towards genes in regulatory and metabolic pathways. As maize is one of the principal models for plant growth and development, this study will serve as a foundation for future research into the functional roles of miRNA genes.