Abscisic Acid-responsive Transcription Factors Research Articles

Abscisic acid-responsive transcription factors PavDof2/6/15 mediate fruit softening in sweet cherry.

Softening is a key step during fruit ripening that is modulated by the interplay between multiple phytohormones. The antagonistic action of abscisic acid (ABA) and auxin determines the rate of fruit ripening and softening. However, the transcription factors that integrate ABA and auxin signals to regulate fruit softening remain to be determined. In this study, we identified several DNA-binding with One Finger (Dof) transcription factors essential for ABA-promoted fruit softening, based on transcriptome analysis of two sweet cherry (Prunus avium L.) varieties with different fruit firmness. We show that PavDof6 directly binds to the promoters of genes encoding cell wall-modifying enzymes to activate their transcription, while PavDof2/15 directly repress their transcription. Transient overexpression of PavDof6 and PavDof2/15 in sweet cherry fruits resulted in precocious and delayed softening, respectively. In addition, we show that the auxin response factor PavARF8, the expression of whose encoding gene is repressed by ABA, activates PavDof2/15 transcription. Furthermore, PavDof2/6/15 and PavARF8 directly bind to the 9-cis-epoxycarotenoid dioxygenase 1 (PavNCED1) promoter and regulate its expression, forming a feedback mechanism for ABA-mediated fruit softening. These findings unveil the physiological framework of fruit softening and establish a direct functional link between the ABA-PavARF8-PavDofs module and cell-wall-modifying genes in mediating fruit softening.

Genome-wide analysis of the AREB/ABF gene lineage in land plants and functional analysis of TaABF3 in Arabidopsis

BackgroundPrevious studies have shown that ABFs (abscisic acid-responsive transcription factors) are important ABA-signaling components that participate in abiotic stress response. However, little is known about the function of ABFs in Triticum aestivum. In addition, although various ABFs have been identified in other species, the phylogenetic relationship between ABF transcription factors has not been systemically investigated in land plants.ResultsIn this study, we systemically collected ABFs from land plants and analyzed the phylogenetic relationship of these ABF genes. The ABF genes are present in all the land plants we investigated, including moss, lycophyte, monocots, and eudicots. Furthermore, these ABF genes are phylogenetically divided into seven subgroups, differentiations that are supported by variation in the gene structure, protein properties, and motif patterns. We further demonstrated that the expression of ABF genes varies among different tissues and developmental stages, and are induced by one or more environmental stresses. Furthermore, we found that three wheat ABFs (TaABF1, TaABF2, and TaABF3) were significantly induced by drought stress. Compared with wild-type (WT) plants, transgenic Arabidopsis plants overexpressing TaABF3 displayed enhanced drought tolerance.ConclusionsThese results provide important ground work for understanding the phylogenetic relationships between plant ABF genes. Our results also indicate that TaABFs may participate in regulating plant response to abiotic stresses.

Thermostability of the PYL–PP2C Heterodimer Is Dependent on Magnesium: In Silico Insights into the Link between Heat Stress Response and Magnesium Deficiency in Plants

Magnesium deficiency increases the susceptibility of plants toward heat stress. The correlation between magnesium levels and stress response has been studied at the physiological level; albeit, the molecular explanation to this relationship remains elusive. Among diverse pathways implicated in the heat stress, the abscisic acid (ABA) signal modulates the heat stress response by magnesium dependent phosphatases (PP2Cs). Exclusively, sequestration of PP2Cs by ABA receptors (PYLs) in the heterodimer form activates the stress response through ABA responsive transcription factors. In this study, the molecular interplay between magnesium levels and ABA related heat stress response was investigated. Molecular dynamics simulations have been applied to two different PYL-PP2C heterodimer systems representing normal and magnesium deficient conditions. The heterodimer conformation and stability were delineated at high temperatures mimicking heat stress. Results showed that the thermostability of the heat stress response heterodimer was significantly dependent on the magnesium. Furthermore, a conserved aromatic cluster at the dimer interface acted synergistically with the metal to confer thermostability to the heterodimer structure. These structural insights into one of the possible links between magnesium levels and stress highlight the importance of metal micronutrients for tuning the stability of the stress-related proteins and optimizing tolerance.