Plant Breeding For Stress Tolerance Research Articles

Overexpression of the autophagy-related gene

Context Salt stress harms plant growth and limits crop productivity. Autophagy is a material decomposition and metabolism pathway that is central to regulating plant responses to environmental stimuli and may be employed in plant breeding for stress tolerance. The autophagy-related gene ATG8 has become an essential tool for monitoring autophagic activity. Aims We aimed to determine the effects of increased autophagic activity via overexpression of ATG8 on tolerance of wheat (Triticum aestivum L.) seedlings to NaCl stress. Methods Salt-tolerant wheat cv. Jimai22 was used to produce TaATG8a-overexpressing wheat seedlings using Foxtail mosaic virus based virus-mediated overexpression technology. TaATG8a-overexpressing seedlings were exposed to NaCl stress for 6 days. Key results Overexpression of TaATG8a enhanced autophagic activity and improved salt stress tolerance of wheat seedlings. Overexpression of TaATG8a also reduced damage to photosystem II, reduced excess accumulation of reactive oxygen species, increased the activities of superoxide dismutase, peroxidase and catalase, and suppressed programmed cell death in wheat seedling leaves during NaCl treatment. Conclusions Overexpression of TaATG8a conferred higher tolerance of wheat seedlings to NaCl stress and suppressed salt-induced programmed cell death, accompanied by increased autophagic activity. Implications This study provides genetic resources and a theoretical basis for stress tolerance breeding in wheat.

Mutation of GmAITR Genes by CRISPR/Cas9 Genome Editing Results in Enhanced Salinity Stress Tolerance in Soybean

Breeding of stress-tolerant plants is able to improve crop yield under stress conditions, whereas CRISPR/Cas9 genome editing has been shown to be an efficient way for molecular breeding to improve agronomic traits including stress tolerance in crops. However, genes can be targeted for genome editing to enhance crop abiotic stress tolerance remained largely unidentified. We have previously identified abscisic acid (ABA)-induced transcription repressors (AITRs) as a novel family of transcription factors that are involved in the regulation of ABA signaling, and we found that knockout of the entire family of AITR genes in Arabidopsis enhanced drought and salinity tolerance without fitness costs. Considering that AITRs are conserved in angiosperms, AITRs in crops may be targeted for genome editing to improve abiotic stress tolerance. We report here that mutation of GmAITR genes by CRISPR/Cas9 genome editing leads to enhanced salinity tolerance in soybean. By using quantitative RT-PCR analysis, we found that the expression levels of GmAITRs were increased in response to ABA and salt treatments. Transfection assays in soybean protoplasts show that GmAITRs are nucleus proteins, and have transcriptional repression activities. By using CRISPR/Cas9 to target the six GmAITRs simultaneously, we successfully generated Cas9-free gmaitr36 double and gmaitr23456 quintuple mutants. We found that ABA sensitivity in these mutants was increased. Consistent with this, ABA responses of some ABA signaling key regulator genes in the gmaitr mutants were altered. In both seed germination and seedling growth assays, the gmaitr mutants showed enhanced salt tolerance. Most importantly, enhanced salinity tolerance in the mutant plants was also observed in the field experiments. These results suggest that mutation of GmAITR genes by CRISPR/Cas9 is an efficient way to improve salinity tolerance in soybean.

DREB2 (dehydration-responsive element-binding protein 2) type transcription factor in sorghum (Sorghum bicolor): genome-wide identification, characterization and expression profiles under cadmium and salt stresses.

Biotic and abiotic stresses negatively affect fitness, biomass production, and crop yield in plants. The dehydration-responsive element-binding proteins (DREB) are important transcription factors (TFs), and are induced by abiotic and biotic stresses. In this study, genome-wide identification, in silico sequence, and phylogenetic analyses and expression analyses of DREB2 genes under cadmium (Cd) and salt (NaCl) stresses in sorghum (Sorghum bicolor, Sb) were performed. Six putative SbDREB2 genes were identified in sorghum genome and all contained AP2 domain (PF00847). Nucleotide diversities in SbDREB2 genes were calculated as π: 0.53 and θ: 0.39, respectively. While exon numbers of them were either one or two, length of SbDREB2 proteins ranged from 238 to 388 amino acid residues. Fifty-six cis-acting regulatory elements, which are tissue specific, light, hormone, and stress responsive, were identified in the promotor regions of SbDREB2 genes. Analyses on digital expression data indicated that SbDREB2A and SbDREB2B are more expressed genes than other SbDREB genes in sorghum. Under Cd and NaCl stresses, expressions of SbDREB2 genes were induced at different levels. All SbDREB2 genes in root were up-regulated under salt stress. In case of Cd stress, SbDREB2D gene was particularly up-regulated in leaves and roots. Co-expression analyses revealed four of TFs in co-expression network, indicating that they have roles in transcriptional cascade. Furthermore, five miRNA target regions were identified for four SbDREB2 genes, indicating their roles in post-transcriptional regulation. The predicted 3D structure of SbDREB2 proteins showed some structural divergences and structure overlap between rice and sorghum varied at between 26.58 and 50%. Finally, obtained data could be used in breeding of stress-tolerant plants, particularly genetically engineered DREB2 expressing plants. Findings in this study would also contribute to the understanding of DREB2 genes in plants, especially in sorghum.

Genomics Researches and Their Applications in Plant Breeding at PAG XXIV Conference

The rise of whole genome sequences of different plants provided more understanding about the gene regulation and genome evolution in further studying plants. More and more pathways and networks are identified by novel gene discoveries. Therefore, the Plant and Animal Genome Conference (PAG XXIV) provides a good venue to share the recent progress in the area of plant research genome sequencing technologies in various plants. However, this information can make a powerful system for developing improved crop varieties. By the way, the genome annotation and assembly is an essential key for breeding of stress-tolerant plants. PAG XXIV demonstrated different works about the extensive use of genomic databases accompanied by bioinformatics tools to accelerate breeding methods, discovery of new approaches to genomics, further increasing biomass of bioenergy crops, and explaining the genetic mechanisms in plant growth and defense. This review article summarizes some of the researches in various plants of rice, corn, wheat, cottonwood, switchgrasses, Thinopyrum, wheatgrass and Arabidopsis presented in PAG XXIV with the focus on genome technologies and their applications in plant breeding.