Abstract
Production and utilization of cassava (Manihot esculenta) is significantly constrained by pests, diseases, poor yields and low nutritional content. Various approaches are currently being applied to mitigate these constraints. However, an aspect of plant developmental genetics little known in cassava is the role that microRNAs (miRNAs) play in gene regulation. miRNAs are 20 - 24 nucleotide long non-protein-coding RNAs that play important roles in post-transcriptional gene silencing in many organisms. Thorough understanding of the mechanisms involved in miRNAs mediated post-transcriptional gene regulation will have implications for crop production improvement. The potential of miRNAs for cassava improvement and also some data obtained on cassava miRNAs using comparative genomics analysis have been briefly discussed. 17 miRNA families and target genes in cassava that are also conserved in other plant species have been revealed. However, the ESTs representing seven of these miRNA families produced foldbacks that show more than 3 nucleotides not involved in canonical base pairing within a loop or bulge in the mature miRNA: RNA* dimer, thus were not considered miRNA secondary structures. Consistent with previous reports, majority of the target genes identified are transcription factors. Other targets appear to play roles in diverse physiological processes. Furthermore, a detailed description and insight into some of the current bioinformatic resources and approaches applicable to cassava have been discussed. Such information will further enhance the rapid discovery and analysis of more novel miRNAs in cassava towards its improvement. Key words: Cassava, microRNAs, target genes, improvement, characterization.
Highlights
Cassava (Manihot esculenta) is one of the most important root crops in Africa
An aspect of plant developmental genetics little known in cassava is the role that microRNAs play in gene regulation. miRNAs are 20 - 24 nucleotide long nonprotein-coding RNAs that play important roles in post-transcriptional gene silencing in many organisms
The potential of miRNAs for cassava improvement and some data obtained on cassava miRNAs using comparative genomics analysis have been briefly discussed. 17 miRNA families and target genes in cassava that are conserved in other plant species have been revealed
Summary
Cassava (Manihot esculenta) is one of the most important root crops in Africa. It has high adaptability to low-fertility soils and is able to withstand erratic rainfall and long drought conditions (Mathews et al, 1993). Accurate detection and expression profiling of these miRNAs will enable a better understanding of their role in plant growth and development (Millar and Gubler, 2005; Rhoades and Bartel, 2004; Jagadeeswaran et al, 2009) Breakthrough in this area is likely to reveal developmental regulation and disease mechanisms related to miRNAs. In an attempt to stimulate more research interest in cassava miRNAs, an overview of miRNAs and some current bioinformatic resources and approaches available for prediction and analysis of plant miRNAs have been discussed. Several recent findings have implicated miRNAs in a number of biological mechanisms including leaf growth (Palatnik et al, 2003), stem growth (Mallory et al, 2004), root growth (Subramanian et al, 2009), floral organ identity, control of female gamete formation and reproductive development (Millar and Gubler, 2005; Olmedo-Monfil et al, 2010), auxin signaling (Rhoades and Bartel, 2004), biotic and abiotic stress response (Jagadeeswaran et al, 2009)
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