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Drought and salinity have become major environmental problems that affect the production of agriculture, forestry and horticulture. The identification of stress-tolerant genes from plants adaptive to harsh environments might be a feasible strategy for plant genetic improvement to address the challenges brought by global climate changes. In this study, a dehydration-upregulated gene MfWRKY7 of resurrection Plant Myrothamnus f labellifolia , encoding a group IId WRKY transcription factor, was cloned and characterized. The overexpression of MfWRKY7 in Arabidopsis increased root length and tolerance to drought and NaCl at both seedling and adult stages. Further investigation indicated that MfWRKY7 transgenic plants had higher contents of chlorophyll, proline, soluble protein, and soluble sugar but a lower water loss rate and malondialdehyde content compared with wild-type plants under both drought and salinity stresses. Moreover, the higher activities of antioxidant enzymes and lower accumulation of O 2 - and H 2 O 2 in MfWRKY7 transgenic plants were also found, indicating enhanced antioxidation capacity by MfWRKY7. These findings showed that MfWRKY7 may function in positive regulation of responses to drought and salinity stresses, and therefore, it has potential application value in genetic improvement of plant tolerance to abiotic stress.

Background: Auxins play key roles in the phytohormone network. Early auxin response genes in the AUX/IAA, SAUR, and GH3 families show functional redundancy, which makes it very difficult to study the functions of individual genes based on gene knockout analysis or transgenic technology. As an alternative, chemical genetics provides a powerful approach that can be used to address questions relating to plant hormones., Results: By screening a small-molecule chemical library of compounds that can induce abnormal seedling and vein development, we identified and characterized a piperazine compound 1-[(4-bromophenoxy) acetyl]-4-[(4-fluorophenyl) sulfonyl] piperazine (ASP). The Arabidopsis DR5::GFP line was used to assess if the effects mentioned were correlated with the auxin response, and we accordingly verified that ASP altered the auxin-related pathway. Subsequently, we examined the regulatory roles of ASP in hypocotyl and root development, auxin distribution, and changes in gene expression. Following ASP treatment, we detected hypocotyl elongation concomitant with enhanced cell elongation. Furthermore, seedlings showed retarded primary root growth, reduced gravitropism and increased root hair development. These phenotypes were associated with an increased induction of DR5::GUS expression in the root/stem transition zone and root tips. Auxin-related mutants including tir1-1, aux1-7 and axr2-1 showed phenotypes with different root-development pattern from that of the wild type (Col-0), and were insensitive to ASP. Confocal images of propidium iodide (PI)-stained root tip cells showed no detectable damage by ASP. Furthermore, RT-qPCR analyses of two other genes, namely, Ethylene Response Factor (ERF115) and Mediator 18 (MED18), which are related to cell regeneration and damage, indicated that the ASP inhibitory effect on root growth was not attributable to toxicity. RT-qPCR analysis provided further evidence that ASP induced the expression of early auxin-response-related genes., Conclusions: ASP altered the auxin response pathway and regulated Arabidopsis growth and development. These results provide a basis for dissecting specific molecular components involved in auxin-regulated developmental processes and offer new opportunities to discover novel molecular players involved in the auxin response.