Sp-miR396a-5p acts as a stress-responsive genes regulator by conferring tolerance to abiotic stresses and susceptibility to Phytophthora nicotianae infection in transgenic tobacco

Abstract

Overexpression of Sp-miR396a-5p in tobacco increased tolerance to salt, drought, cold stress and susceptibility to Phytophthora nicotianae infection. MicroRNA396 (miR396) is one of the conserved microRNA families in plants, and it targeted growth-regulating factors (GRFs) family. The GRF transcription factors are associated with growth and stress responses. However, the molecular mechanisms of miR396 responding to environmental stresses are elusive. The purpose of this study was to explore the function of tomato miR396a-5p (Sp-miR396a-5p) in Solanaceae responses to abiotic and biotic stresses. We showed that Sp-miR396a-5p transcript levels were up-regulated under salt and drought stresses and down-regulated after Phytophthora infestans (P. infestans) infection. Consistently, overexpression of Sp-miR396a-5p in tobacco enhanced its tolerance to salt, drought and cold stresses. Additionally, the expression of Sp-miR396a-5p was found to be down-regulated under pathogen-related biotic stress. Tobacco plants overexpressing Sp-miR396a-5p showed increased susceptibility to Phytophthora nicotianae (P. nicotianae) infection. Physiological analysis indicated that Sp-miR396a-5p overexpression enhanced osmoregulation and decreased production of reactive oxygen species (ROS). Furthermore, four Sp-miR396a-5p target genes, NtGRF1, NtGRF3, NtGRF7 and NtGRF8, were down-regulated in these plants. Our results suggested that Sp-miR396a-5p plays critical roles in both abiotic stresses through targeting NtGRF7-regulated expression of osmotic stress-responsive genes and pathogen infection via the regulatory networks of NtGRF1 and NtGRF3.

The Arabidopsis miR396 mediates pathogen-associated molecular pattern-triggered immune responses against fungal pathogens

“…Also, different stresses lead to changes in miR396 accumulation, including interactions with nematodes, bacteria, oomycetes and abiotic stress, among others2844575859. However, little is known about the miR396-mediated molecular reprogramming in those different scenarios.…”

“…Fungal perception impinges on the activity of MIR396 promoters leading to a gradual decline in mature miR396 levels and a concomitant increase of miR396 target expression during the normal course of PTI. MiR396 targets can regulate growth and stress responses2425262728, MIM396 plants grow and develop normally. This result is in agreement with the minor changes observed in the global transcriptome in non-pathogen challenged MIM396 plants.…”

MiR1918 enhances tomato sensitivity to Phytophthora infestans infection

“…For instance, our previous work has shown that the miR396 family miRNAs target growth-regulating factor (GRF) genes. Tobacco plants overexpressing Sp -miR396a-5p show increased susceptibility to P. nicotianae infection38. Although plant miRNAs have been extensively studied, few miRNAs have been discovered in microbes.…”

“…After 4 days, the leaves were collected for RNA extraction to examine the expression levels of pi-amiR1918 and target genes. After 7 days, the relative lesion size, sporangia per leaf, and detection of dead cells were determined by ImageJ, direct counting and trypan Blue staining38, respectively.…”

Emerging techniques to decipher microRNAs (miRNAs) and their regulatory role in conferring abiotic stress tolerance of plants

“…The transgenic lines under multiple stresses launched an efficient antioxidative system involving up-regulation of CSD1, CSD2, CCS1, glutathione-S-transferase, as well as the redox stress-associated gene, SAP12 (Ma et al 2015). Chen et al (2015) described tomato miR396a-5p as a positive regulator of tolerance against multiple abiotic stresses, but a negative regulator of generating resistance against Phytophthora infestans. Overexpression of miR396a-5p from tomato in tobacco increased plant tolerance towards salinity, drought, and cold stresses primarily by targeting growth-regulating factors (GRFs).…”