Transgenic sugarcane with higher levels of BRK1 showed improved drought tolerance

Transgenic sugarcane overexpressing Glyoxalase III improved germination and biomass production at formative stage under salinity and water-deficit stress conditions

The glyoxalase system, involving Glyoxalase I (GlyI) and Glyoxalase II (Gly II), plays a vital role in abiotic stress tolerance in plants. A novel enzyme Glyoxalase III (Gly III) was found recently from bacteria, yeast, and plant species. This enzyme provides a new way to detoxify Methylglyoxal (MG), a cytotoxic α-oxoaldehyde, which, in excess, can cause complete cell destruction by forming Reactive Oxygen Species (ROS) and Advanced Glycation End products (AGEs) or DNA/RNA mutation. In this background, the current study examined sugarcane transgenic events that exhibit an increase in expression of EaGly III, to assess their performance in terms of germination and biomass production during formative stage under stress conditions. Southern blot analysis outcomes confirmed the integration of transgene in the transgenic plants. The results from quantitative RT-PCR analyses confirmed high expression levels of EaGly III in transgenic events compared to wild type (WT) under salinity (100 and 200 mM NaCl) and drought (withholding watering) conditions. Transgenic events exhibited enhanced biomass productivity ranged between 0.141 Kg/pot and 0.395 Kg/pot under 200 mM salinity and 0.262 Kg/pot and 0.666 Kg/pot under drought stress. Further, transgenic events observed significantly higher germination rates under salinity and drought conditions compared to that of WT. Subcellular localization prediction by EaGlyIII-GFP fusion expression in sugarcane callus showed that it is distributed across the cytoplasm, thus indicating its widespread activity within the cell. These results strongly suggest that enhancing EaGly III activity is a useful strategy to improve the salinity and drought-tolerance in sugarcane as well as other crops.

Isolation and Characterization of Erianthus arundinaceus Phosphate Transporter 1 (PHT1) Gene Promoter and 5' Deletion Analysis of Transcriptional Regulation Regions under Phosphate Stress in Transgenic Tobacco

Phosphorus deficiency highly interferes with plant growth and development. Plants respond to persistent P deficiency by coordinating the expression of genes involved in the alleviation of stress. Promoters of phosphate transporter genes are a great choice for the development of genetically modified plants with enhanced phosphate uptake abilities, which improve crop yields in phosphate-deficient soils. In our previous study, the sugarcane phosphate transporter PHT1;2 gene showed a significantly high expression under salinity stress. In this study, the Erianthus arundinaceus EaPHT1;2 gene was isolated and characterized using various in silico tools. The deduced 542 amino acid residues have 10 transmembrane domains, with a molecular weight and isoelectric point of 58.9 kDa and 9.80, respectively. They displayed 71-96% similarity with Arabidopsis thaliana, Zea mays, and the Saccharum hybrid. To elucidate the function of the 5' regulatory region, the 1.1 kb promoter was isolated and validated in tobacco transgenics under Pi stress. The EaPHT1;2 promoter activity was detected using a β-glucuronidase (GUS) assay. The EaPHT1;2 promoter showed 3- to 4.2-fold higher expression than the most widely used CaMV35S promoter. The 5' deletion analysis with and without 5' UTRs revealed a small-sized 374 bp fragment with the highest promoter activity among 5' truncated fragments, which was 2.7 and 4.2 times higher than the well-used CaMV35S promoter under normal and Pi deprivation conditions, respectively. The strong and short promoter of EaPHT1;2 with 374 bp showed significant expression in low-Pi-stress conditions and it could be a valuable source for the development of stress-tolerant transgenic crops.

Coordination of m6A mRNA Methylation and Gene Transcriptome in Sugarcane Response to Drought Stress

The N6-methyladenosine (m6A) methylation of mRNA is involved in biological processes essential for plant growth. To explore the m6A modification of sugarcane and reveal its regulatory function, methylated RNA immunoprecipitation sequencing (MeRIP-seq) was used to construct the m6A map of sugarcane. In this study, m6A sites of sugarcane transcriptome were significantly enriched around the stop codon and within 3'-untranslated regions (3'UTR). Gene ontology (GO) analysis showed that the m6A modification genes are associated with metabolic biosynthesis. In addition, the m6A modification of drought-resistant transcript mRNA increased significantly under drought (DR) treatment, resulting in enhanced mRNA stability, which is involved in regulating sugarcane drought resistance. GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment results showed that differentially methylated peak (DMP) modification of differentially expressed genes (DEGs) in DR were particularly associated with abscisic acid (ABA) biosynthesis. The upregulated genes were significantly enriched in the ABA metabolism, ethylene response, fatty acid metabolism, and negative regulation of the abscisic acid activation signaling pathway. These findings provide a basis and resource for sugarcane RNA epigenetic studies and further increase our knowledge of the functions of m6A modifications in RNA under abiotic stress.