Functions of plant WRKY transcription factors in nutrient uptake and utilization as well as detoxification of heavy metals

WRKY proteins are a group of important transcriptional regulators that are unique to plants. WRKY specifically bind with the W-box cis-elements in the promoters of downstream genes to induce or inhibit the transcription and expression of related genes, to regulate plant growth and development, as well as responses to biotic and abiotic stresses. The WRKY gene family is large in number, there are 74 identified WRKY genes 74 in Arabidopsis genome, 182 genes in soybean genome and 109 genes in rice genome, respectively. WRKY genes play pivotal roles in plant response to various biological and abiotic stresses such as drought, salinity, high temperature, nutrient deficiencies, and pathogen infection. Up to now, it has been proved that the AtWRKY45 and AtWRKY75 are involved in regulating the responses of Arabidopsis to low P stress, GmWRKY142 positively regulates the tolerance of Arabidopsis to Cd stress. When exposure to stress, the plant WRKY protein specifically binds to the W-box cis-element in the conserved region of the related gene promoter, thereby achieves self-regulation or cross regulation, then activates or inhibits the transcriptional expression of downstream genes in response to various stress conditions. Numerous downstream target genes have also been revealed consequently, such as the PHT family members related to P nutrition; three AtWRKY genes and six GmWRKY genes are involved in regulating plant nitrogen uptake and utilization; six AtWRKY genes, ten GmWRKY genes, and five OsWRKY genes regulate plant response to phosphorus deficiency; two AtWRKY genes and six GmWRKY genes affect plant potassium absorption and utilization; three GmWRKY genes are involved in regulating the absorption and utilization of sulfate; oneAtWRKY gene is involved in regulating the uptake and utilization of boron; one AtWRKY gene and one OsWRKY gene are involved in regulating plant iron absorption; seven AtWRKY genes, one GmWRKY gene, and one OsWRKY gene are involved in mitigating cadmium toxicity; two AtWRKY genes, two GmWRKY genes, and one OsWRKY gene participate in helping plants detoxify aluminum toxicity. The foci of future researches are: 1) mining new WRKY transcription factors that regulate nutrient uptake and utilization and the downstream genes; 2) decoding the regulation of nutrient-related WRKYs at the translation and post-translation level; 3) determining the transcription of nutrient-related WRKY at epigenetic level; 4) revealing the proteins that interact with WRKY and the underlying mechanisms under nutrient deficiency.