Abstract
Small RNA (sRNA) population in plants comprises of primarily micro RNAs (miRNAs) and small interfering RNAs (siRNAs). MiRNAs play important roles in plant growth and development. The miRNA-derived secondary siRNAs are usually known as phased siRNAs, including phasiRNAs and tasiRNAs. The miRNA and phased siRNA biogenesis mechanisms are highly conserved in plants. However, their functional conservation and diversification may differ in maize. In the past two decades, lots of miRNAs and phased siRNAs have been functionally identified for curbing important maize agronomic traits, such as those related to developmental timing, plant architecture, sex determination, reproductive development, leaf morphogenesis, root development and nutrition, kernel development and tolerance to abiotic stresses. In contrast to Arabidopsis and rice, studies on maize miRNA and phased siRNA biogenesis and functions are limited, which restricts the small RNA-based fundamental and applied studies in maize. This review updates the current status of maize miRNA and phased siRNA mechanisms and provides a survey of our knowledge on miRNA and phased siRNA functions in controlling agronomic traits. Furthermore, improvement of those traits through manipulating the expression of sRNAs or their targets is discussed.
Highlights
Plant and animal small RNAs are short noncoding regulatory RNAs in the size range of ~20 to 30 nucleotides [1,2]
This review examines the current status of our understanding of the biogenesis and functions of micro RNAs (miRNAs) and phased small interfering RNAs (siRNAs) in maize, with a focus on their key components and the missing links of the pathways
We review the identified miRNA and phased siRNA functions in regulating important agronomic traits in maize
Summary
Plant and animal small RNAs (sRNAs) are short noncoding regulatory RNAs in the size range of ~20 to 30 nucleotides (nt) [1,2]. Compared to animal miRNAs, plant miRNAs tend to have fewer targets that mainly encode transcription factors and F-box proteins [8] This indicates that miRNA is at the central position of gene expression regulatory networks of plant growth and development. There have been limited studies on the roles of miRNAs and miRNA-derived secondary siRNAs in maize metabolism, development and stress responses [12,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34], making it far from utilized in agronomic traits improvement through genetic engineering. We discuss the potential applications of these small regulatory RNAs or of their target genes in agronomic traits enhancement
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