Saminathan Subburaj

Identification of novel stress-induced microRNAs and their targets in Camelina sativa using computational approach

MicroRNAs (miRNAs) are a class of small non-coding, single-stranded RNA sequences that regulate gene expression at the post-transcriptional level and also reported to function in stress responses, but their role has not been studied in Camelina (Camelina sativa L.), an emerging oil crop. In this study, we predicted conserved as well as putative novel miRNAs from a Camelina drought stress cDNA library using comprehensive genomic approaches. Based on the sequence homology, we predicted 145 miRNAs, of which 61 were conserved, and 84 putative novel miRNAs were found to belong to 26 and 72 different miRNA families, respectively. In silico expression analysis indicated that 20 miRNAs were really expressed in Camelina genome, and several of them have tissue-specific expression character. We found that the 60 putative novel miRNA families target 117 genes. Most of the miRNA targets were predicted to genes including that regulate stress response, transcription factors, and fatty acid and lipid metabolism-related genes. Expression patterns of 6 randomly selected miRNAs under drought stress were validated by real-time quantitative polymerase chain reaction analysis. Coordinated expression changes between 6 randomly selected miRNAs and their target genes, suggested that the predicted miRNAs could be drought-responsive and that they would likely be directly involved in stress regulatory networks of Camelina. These results indicate that, in C. sativa, under drought stress, a large number of new miRNAs could be discovered, and the predicted stress-responsive miRNAs and their target transcripts will serve as valuable resources for future studies.

Targeted genome editing, an alternative tool for trait improvement in horticultural crops

Improving crops through plant breeding, an important approach for sustainable agriculture, has been utilized to increase the yield and quality of foods and other biomaterials for human use. Crops, including cereals, vegetables, ornamental flowers, fruits, and trees, have long been cultivated to produce high-quality products for human consumption. Conventional breeding technologies, such as natural cross-hybridization, mutation induction through physical or chemical mutagenesis, and modern transgenic tools are often used to enhance crop production. However, these breeding methods are sometimes laborious and complicated, especially when attempting to improve desired traits without inducing pleiotropic effects. Recently, targeted genome editing (TGE) technology using engineered nucleases, including meganucleases, zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeat (CRISPR) nucleases, has been used to improve the traits of economically important plants. TGE has emerged as a novel plant-breeding tool that represents an alternative approach to classical breeding, but with higher mutagenic efficiency. Here, we briefly describe the basic principles of TGE and the types of engineered nucleases utilized, along with their advantages and disadvantages. We also discuss their potential use to improve the traits of horticultural crops through genome engineering.

Identification of γ-radiation-responsive microRNAs and their target genes in Tradescantia (BNL clone 4430)

MicroRNAs (miRNAs) are endogenous small non-coding RNAs that regulate gene expression at posttranscriptional level. They might regulate tolerance to abiotic stress. However, this has not been studied in Tradescantia (BNL clone 3340), an important bio-indicator for measuring the effect of radiation. Up to date, gamma irradiation (γ-IR) responsive miRNAs and their expressions patterns in plants in response to γ-IR stress have not been reported yet. Therefore, putative γ-IR responsive miRNAs from a cDNA library of Tradescantia after radiation stress were predicted in this study by using comprehensive genomic approaches. Here, we identified 37 miRNAs belonged to 36 different miRNA families. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis of five randomly selected miRNAs were confirmed that their responsiveness to γ-IR stress. Target prediction revealed that 37 miRNAs targeted 149 genes involved in stress tolerance regulation, light response, redox systems, signaling pathways, DNA repair, and transcription factors. A coordinated reverse expression changes between miRNAs and their target genes further validated that these predicted miRNAs could be γ-IR responsive and likely to be directly involved in stress regulatory networks of Tradescantia. Altogether, these results will provide novel insights to the understanding of molecular mechanisms of miRNAs involved in plant response to γ-IR.

Expression profile of defense-related genes in response to gamma radiation stress Nuri Park

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Tradescantia is a perennial plant in the family of Commelinaceae. It is known to be sensitive to radiation. In this study, Tradescantia BNL 4430 was irradiated with gamma radiation at doses of 50 to 1,000 mGy in a phytotron equipped with a 60 Co radiation source at Korea Atomic Energy Research Institute, Korea. At 13 days after irradiation, we extracted RNA from irradiated floral tissues for RNA-seq. Transcriptome assembly produced a total of 77, 326 unique transcripts. In plantlets exposed to 50, 250, 500, and 1000 mGy, the numbers of up-regulated genes with more than 2fold of expression compared that in the control were 116, 222, 246, and 308, respectively. Most of the up-regulated genes induced by 50 mGy were heat shock proteins (HSPs) such as HSP 70, indicating that protein misfolding, aggregation, and translocation might have occurred during radiation stress. Similarly, highly up-regulated transcripts of the IQ-domain 6 were induced by 250 mGy, KAR-UP oxidoreductase 1 was induced by 500 mGy, and zinc transporter 1 precursor was induced by 1000 mGy. Reverse transcriptase (RT) PCR and quantitative real time PCR (qRT-PCR) further validated the increased mRNA expression levels of selected genes, consistent with DEG analysis results. However, 2.3 to 97fold higher expression activities were induced by different doses of radiation based on qRT-PCR results. Results on the transcriptome of Tradescantia in response to radiation might provide unique identifiers to develop in situ monitoring kit for measuring radiation exposure around radiation facilities.