Title : Identification and characterization of microRNAs as role players in the wheat (Triticum aestivum) defence response against the Russian wheat aphid
Abstract:
Wheat (Triticum aestivum L.) is one of the most dominant crops for human and livestock feed. Yields of wheat have declined worldwide due to pathogens and pests. Diuraphis noxia (Russian wheat aphid, RWA) is the most devastating aphid pest affecting wheat cultivation in South Africa and other regions. Feeding by this insect causes the appearance of severe symptoms, including necrosis, streaking and trapping of the heads of the wheat plant. This reduces crop yield and can lead to the death of susceptible cultivars. The use of resistant cultivars against the RWA is being negated by the emergence of resistance-breaking biotypes. Feeding by the RWA on wheat induces differential expression of microRNA genes. Thus, this study aimed to use next-generation sequencing to identify a larger pool of microRNAs and to further characterize them and their putative targets. In this study, 12 microRNA libraries (3 bioreps) from Tugela uninfested, Tugela Dn uninfested, Tugela infested and Tugela Dn infested were constructed respectively. The expression of candidate miRNAs and their targets was determined by quantitative real-time PCR. The predicted target genes were analysed for their gene ontology placement to determine their biological roles in plants. A total of 503 miRNA candidates were obtained, and only 87 of these matched the known Triticum aestivum miRNA. The identified miRNAs seem to target known resistance gene family members and previously identified resistance responses from wheat after infestation by the RWA. The gene ontology results indicated that most of the identified targets in this study play a role to regulate some biological pathways that are known to be regulated during wheat-RWA interaction. The use of the next- generation sequencing method has boosted small RNA discoveries at an unprecedented scale. However, only a few out of several thousand discovered small RNAs have been functionally characterised. The field of small RNA functional genomics research is still in its early phase and in the case of complex crops like Triticum aestivum the progress is even slower. More work needs to be done to characterize more miRNAs. The identification and characterisation of more small RNA and their target genes will contribute to our understanding of wheat and RWA interaction. Once a better understand of this interaction is achieved then this knowledge can be utilised in the future production of crops with better resistance against RWA.
