ABSTRACT
MicroRNAs (miRNAs), a type of short noncoding RNA molecule (21-23 nucleotides), mediate repressive gene regulation through RNA silencing at the posttranscriptional level and play an important role in the defense response to abiotic and biotic stresses. miRNAs of the plant system have been studied in model crops for their diverse regulatory role while less is known about their significance in other plants whose genome and transcriptome data are scarce in the database, including eggplant (Solanum melongena L.). In the present study, a next-generation sequencing platform was used for the sequencing of miRNA, and real-time quantitative PCR for miRNAs was used to validate the gene expression patterns of miRNAs in Solanum melongena plantlets infected with the bacterial wilt-causing pathogen Ralstonia solanacearum (R. solanacearum). Sequence analyses showed the presence of 375 miRNAs belonging to 29 conserved families. The miR414 is highly conserved miRNA across the plant system while miR5658 and miR5021 were found exclusively in Arabidopsis thaliana surprisingly, these miRNAs were found in eggplants too. The most abundant families were miR5658 and miR414. Ppt-miR414, hvu-miR444b, stu-miR8020, and sly miR5303 were upregulated in Pusa purple long (PPL) (susceptible) at 48 h postinfection, followed by a decline after 96 h postinfection. A similar trend was obtained in ath-miR414, stu-mir5303h, alymiR847-5p, far-miR1134, ath-miR5021, ath-miR5658, osa-miR2873c, lja-miR7530, stu-miR7997c, and gra-miR8741 but at very low levels after infection in the susceptible variety, indicating their negative role in the suppression of host immunity. On the other hand, osa-miR2873c was found to be slightly increased after 96 hpi from 48 hpi. Most of the miRNAs under study showed relatively lower expression in the resistant variety Arka Nidhi after infection than in the susceptible variety. These results shed light on a deeper regulatory role of miRNAs and their targets in regulation of the plant response to bacterial infection. The present experiment and their results suggested that the higher expression of miRNA leads to a decline in host mRNA and thus shows susceptibility.
ABSTRACT
Halophiles are a class of microorganisms that thrive in environments with very high salt concentrations. The coastal regions of Saurashtra Gujarat host a diverse group of microorganisms including halophilic and halotolerant bacteria that may have plant growth promoting characteristics. Microorganisms with plant growth promoting characteristics are of immense importance in the field of agriculture and the present study was conducted to investigate the characteristics of halophilic and halotolerant bacteria isolated from agricultural soils of coastal regions of Junagadh and Porbandar districts of Saurashtra, Gujarat. A total of 15 isolated strains showed indole acetic acid production, solubilization of phosphate and potash, and nitrogen fixing capacity ranging from 18.77-33.48 µg ml-1, 50.10-106.10%, 180.42-239.92% and 0.170-0.480 g kg-1 of Jensen's agar medium, respectively, while two isolates were also found positive for siderophore production. Besides, nine out of fifteen isolates also showed positive ACC deaminase activity ranging from 0.92-5.78 µM α-ketobutyrate mg-1 h-1. The isolates were further characterized by physiological, microscopic, and biochemical tests. The halophilic and halotolerant bacterial isolates were identified by 16S rRNA gene sequencing as belonging to Halomonas pacifica, H. stenophila, and Bacillus haynesii, B. licheniformis and Oceanobacillus aidingensis respectively. The 16S rRNA partial gene sequence of two isolates belonging to H. pacifica and H. stenophila were submitted to NCBI with accession number MK955347 and MK961217 respectively. The findings of the present investigation showed that isolated bacterial halophiles possess promising plant growth promoting characteristics. Their potential as bioinoculants to alleviate salinity stress in crops and for bioremediation deserves further investigation.
