Abstract
Transcription factors (TFs) are master regulators of abiotic stress responses in plants. This review focuses on TFs from seven major TF families, known to play functional roles in response to abiotic stresses, including drought, high salinity, high osmolarity, temperature extremes and the phytohormone ABA. Although ectopic expression of several TFs has improved abiotic stress tolerance in plants, fine-tuning of TF expression and protein levels remains a challenge to avoid crop yield loss. To further our understanding of TFs in abiotic stress responses, emerging gene regulatory networks based on TFs and their direct targets genes are presented. These revealed components shared between ABA-dependent and independent signaling as well as abiotic and biotic stress signaling. Protein structure analysis suggested that TFs hubs of large interactomes have extended regions with protein intrinsic disorder (ID), referring to their lack of fixed tertiary structures. ID is now an emerging topic in plant science. Furthermore, the importance of the ubiquitin-proteasome protein degradation systems and modification by sumoylation is also apparent from the interactomes. Therefore; TF interaction partners such as E3 ubiquitin ligases and TF regions with ID represent future targets for engineering improved abiotic stress tolerance in crops.
Highlights
Plants are constantly being exposed to abiotic stresses such as drought, high salinity, high osmolarity, threshold temperatures, nutrient deficiency, oxidation, and changing light conditions.These environmental stress factors negatively affect growth and productivity, and plants have evolved different mechanisms to respond to such challenges
WRKY70 is critical for effective defense against pathogen attack and a key regulator in the antagonistic interaction between salicylic acid (SA) and jasmonic acid (JA) [188], and likely to play an important role in abiotic stress responses
Ectopic expression of specific transcription factors (TFs) with the purpose of improving stress tolerance has been successful in different crop species [10,13,36,53,76]
Summary
Plants are constantly being exposed to abiotic stresses such as drought, high salinity, high osmolarity, threshold temperatures, nutrient deficiency, oxidation, and changing light conditions. In plant genomes approximately 7% of the coding sequences are assigned to transcription factors (TFs) [4], and many of these are immediate-early abiotic stress-responsive genes [5] These TFs probably initiate the indirect-late phase of responses by binding to cis-acting elements in the promoters of specific target genes encoding proteins with specific functions in for example protein turnover, the dehydration response and cell wall modifications [5]. Some of these TFs are master regulators of signaling and regulatory pathways of stress adaptation, and genetic engineering of one or a few of these may be sufficient to enhance stress tolerance in plants, making these TFs attractive targets for engineering [6].
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