Abstract
MicroRNAs (miRNAs), a class of small non-coding regulatory RNAs, are key molecules in many biological and metabolic processes of plant growth, development and stress response via targeting mRNAs. The phloem-feeding insect whitefly Bemisia tabaci (Hemiptera, Aleyrodidae) is a serious pest that causes devastating harm to agricultural production worldwide. However, the function of host miRNAs in the response to whitefly infestation remains unclear. Here, we sequenced the small RNA and degradome of tobacco (Nicotiana tabacum L.), after and before infestation by B. tabaci. We identified 1291 miRNAs belonging to 138 miRNA families including 706 known miRNAs and 585 novel miRNAs. A total of 47 miRNAs were differentially expressed, of which 30 were upregulated and 17 were downregulated by whitefly exposure. Then, computational analysis showed that the target genes of differential miRNAs were involved in R gene regulation, plant innate immunity, plant pathogen defense, the plant hormone signal pathway and abiotic stress tolerance. Furthermore, degradome analysis demonstrated that 253 mRNAs were cleaved by 66 miRNAs. Among them, the targets cleaved by upregulated miR6025, miR160, miR171, miR166 and miR168 are consistent with our prediction, suggesting that pathogen-related miRNAs may function in plant defense against whitefly. Moreover, our results show that plant miRNA response and miRNA-mediated post-transcriptional regulation for phloem-feeding insect infestation are similar to pathogen invasion. Our study provides additional data to further elucidate how host plants respond and defend the phloem-feeding insects.
Highlights
MicroRNA is a class of non-coding RNA 18–25 nucleotides in length and with endogenous regulatory functions in eukaryotes, and it can regulate gene expression posttranscriptionally via targeting mRNAs for degradation and/or translational inhibition [1].In plants, miRNAs act as the master regulators of growth and development but are involved in the regulation of phenotypic plasticity trigged by various environmental stress [2]
To identify miRNAs that respond to B. tabaci, six sRNA libraries were constructed from leaves of N. tabacum without treatment (Control, n = 3) and infested by B. tabaci (Infested, n = 3)
We found the target genes of upregulated miRNAs were related to the auxin-activated signaling pathway, plant–pathogen interaction, plant hormone signal transduction and so on (Figure S1), while those of downregulated miRNAs were related to positive regulation of circadian rhythm, the far-red signal pathway, cysteine and methionine and so on (Figure S2)
Summary
MicroRNA (miRNA) is a class of non-coding RNA 18–25 nucleotides in length and with endogenous regulatory functions in eukaryotes, and it can regulate gene expression posttranscriptionally via targeting mRNAs for degradation and/or translational inhibition [1].In plants, miRNAs act as the master regulators of growth and development but are involved in the regulation of phenotypic plasticity trigged by various environmental stress [2]. They insert stylets between cells to minimize the damage to plants and avoid induction of the wounding response induced by tissue-chewing insects. These insects release effector proteins into host tissues and trigger ETI [5]. Plants respond to these insects by mobilizing a series of specific defense responses that are regulated by miRNAs. In rice, the biosynthesis genes of JA associated with resistance to brown planthopper (Nilaparvata lugens; BTH) can be modulated by a master plant ontogenetic regulator miR156, indicating miRNAs are involved in the regulation of the plant defense against insects [6]
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