High temperature associated microRNAs and their potential roles in mediating heat tolerance in the leaf of banana inoculated with Serendipita indica

Serendipita indica (S. indica) is an endophytic root fungus that sustains the growth and enhances tolerance of plants to biotic and abiotic stresses. However, little is known on the symbiosis mediated high temperature stress (HT) tolerance regulated at microRNAs (miRNAs) level. In this study, we have elucidated the impact of miRNAs in regulating the S. indica-mediated heat tolerance in the leaves of 'Tianbao' banana (Musa acuminata cv.). The small RNA (sRNA) sequence analysis of the leaves of 'Tianbao' banana inoculated and exposed to HT of 45 degrees C established a set of 278 differentially abundant miRNAs in response to HT stress. These included 185 known miRNAs differentially expressed (DE) and 93 novel miRNAs. GO and KEGG analysis showed that the DE miRNAs were significantly associated with nutrient sources uptake, secondary metabolism, growth regulators, auxin-responsive factor, signal transduction pathways. In summary, our study revealed that miRNA play important regulatory roles during the banana-HT tolerance by regulating the genes involved in heat shock protein, peroxidase, transcription factor, phenylalanine, sucrose synthase, protein kinase, 7-hydroxymethyl chlorophyll. Our result unravelled a framework for future functional analysis of selected miRNAs and their targets in response to HT stress, which may contribute towards the future development of S. indica application to plants.