Genetic Approaches to Enhance Multiple Stress Tolerance in Maize

The multiple-stress effects on plant physiology and gene expression are being intensively studied lately, primarily in model plants such as Arabidopsis, where the effects of six stressors have simultaneously been documented. In maize, double and triple stress responses are obtaining more attention, such as simultaneous drought and heat or heavy metal exposure, or drought in combination with insect and fungal infestation. To keep up with these challenges, maize natural variation and genetic engineering are exploited. On one hand, quantitative trait loci (QTL) associated with multiple-stress tolerance are being identified by molecular breeding and genome-wide association studies (GWAS), which then could be utilized for future breeding programs of more resilient maize varieties. On the other hand, transgenic approaches in maize have already resulted in the creation of many commercial double or triple stress resistant varieties, predominantly weed-tolerant/insect-resistant and, additionally, also drought-resistant varieties. It is expected that first generation gene-editing techniques, as well as recently developed base and prime editing applications, in combination with the routine haploid induction in maize, will pave the way to pyramiding more stress tolerant alleles in elite lines/varieties on time.

The OsERF115/AP2EREBP110 Transcription Factor Is Involved in the Multiple Stress Tolerance to Heat and Drought in Rice Plants

The AP2/EREBP family transcription factors play important roles in a wide range of stress tolerance and hormone signaling. In this study, a heat-inducible rice ERF gene was isolated and functionally characterized. The OsERF115/AP2EREBP110 was categorized to Group-IIIc of the rice AP2/EREBP family and strongly induced by heat and drought treatment. The OsERF115/AP2EREBP110 protein targeted to nuclei and suppressed the ABA-induced transcriptional activation of Rab16A promoter in rice protoplasts. Overexpression of OsERF115/AP2EREBP110 enhanced thermotolerance of seeds and vegetative growth stage plants. The OsERF115/AP2EREBP110 overexpressing (OE) plants exhibited higher proline level and increased expression of a proline biosynthesis P5CS1 gene. Phenotyping of water use dynamics of the individual plant indicates that the OsERF115/AP2EREBP110-OE plant exhibited better water saving traits under heat and drought combined stress. Our combined results suggest the potential use of OsERF115/AP2EREBP110 as a candidate gene for genetic engineering approaches to develop heat and drought stress-tolerant crops.

In search of mutants for gene discovery and functional genomics for multiple stress tolerance in rice.

Mutation breeding is a commanding tool, which has been adapted to generate altered genetic material to study functional genomics, including understanding the molecular basis of stress tolerance. Hitherto, several rice lines have been generated through mutagenesis and the mutated genes responsible for the 'gain of function' in terms of plant architecture, stress tolerance, disease resistance and grain quality have been characterized. Oryza sativa L. cv. IR64 is a high-yielding rice cultivar but sensitive to abiotic stresses such as acute temperatures, salinity and drought. In this study, a population of rice IR64 mutants was generated using gamma irradiation. The population was then subjected to a preliminary phenotypic screening under abiotic stresses such as heat and salinity at the seedling stage. On the basis of root length, shoot length, fresh weight, dry weight and chlorophyll measurements, we identified eight 'gain-of-function' mutant lines and used them for further biochemical and molecular characterization. Phenotyping results demonstrated that the identified mutant plants have gained the potential to thrive under heat and salinity conditions. This information would be of wide scientific interest and helpful for developing novel cultivars able to maintain yield in saline, hot and dry areas.

Heterologous expression of a plant WRKY protein confers multiple stress tolerance in E. coli Bir bitkinin heterolog ifadesi WRKY proteini çoklu stres yaratır E. coli’de tolerans

ObjectiveOsWRKY71, a WRKY protein from rice, is reported to function during biotic stresses. It is requisite to further enquire the efficiency and mechanism of OsWRKY71 under various environmental stresses. Stress indicators such as salt, cold, heat, and drought were studied by overexpressing the OsWRKY71 in E. coli.Materials and methodsDNA binding domain containing region of OsWRKY71 was cloned and expressed in E. coli followed by exposure to stress conditions. OsWRKY71 was also assessed for its role in abiotic stresses in rice by qPCR.ResultsRecombinant E. coli expressing OsWRKY71 was more tolerant to stresses such as heat, salt and drought in spot assay. The tolerance was further confirmed by monitoring the bacterial growth in liquid culture assay demonstrating that it encourages the E. coli growth under salt, drought, and heat stresses. This tolerance may be the consequence of OsWRKY71 interaction with the promoter of stress related genes or with other proteins in bacteria. The RT-qPCR analysis revealed the up-regulation of OsWRKY71 gene in rice upon interaction to cold, salt, drought and wounding with maximum up-regulation against salinity.ConclusionThus, the defensive role of OsWRKY71 may accord to the development and survival of plants during different environmental stresses.