Arabidopsis ABF3 and ABF4 Transcription Factors Act with the NF-YC Complex to Regulate SOC1 Expression and Mediate Drought-Accelerated Flowering

Drought Resistance by Engineering Plant Tissue-Specific Responses

Drought is the primary cause of agricultural loss globally, and represents a major threat to food security. Currently, plant biotechnology stands as one of the most promising fields when it comes to developing crops that are able to produce high yields in water-limited conditions. From studies of Arabidopsis thaliana whole plants, the main response mechanisms to drought stress have been uncovered, and multiple drought resistance genes have already been engineered into crops. So far, most plants with enhanced drought resistance have displayed reduced crop yield, meaning that there is still a need to search for novel approaches that can uncouple drought resistance from plant growth. Our laboratory has recently shown that the receptors of brassinosteroid (BR) hormones use tissue-specific pathways to mediate different developmental responses during root growth. In Arabidopsis, we found that increasing BR receptors in the vascular plant tissues confers resistance to drought without penalizing growth, opening up an exceptional opportunity to investigate the mechanisms that confer drought resistance with cellular specificity in plants. In this review, we provide an overview of the most promising phenotypical drought traits that could be improved biotechnologically to obtain drought-tolerant cereals. In addition, we discuss how current genome editing technologies could help to identify and manipulate novel genes that might grant resistance to drought stress. In the upcoming years, we expect that sustainable solutions for enhancing crop production in water-limited environments will be identified through joint efforts.

Expression of Three Related to ABI3/VP1 Genes in Medicago truncatula Caused Increased Stress Resistance and Branch Increase in Arabidopsis thaliana

Related to ABSCISIC ACID INSENSITIVE3 (ABI3)/VIVIPAROUS1(VP1)(RAV) transcription factors, which encode a B3 domain and an APETALA2(AP2) domain, belong to the APETALA2/ethylene-responsive element binding factor(AP2/ERF) or B3 superfamily and play an important role in regulating plant growth and development and responding to abiotic stress. Although there have been many functional studies on RAV, the functional differences between RAVs are not clear. Therefore, in this study, the functional differences of RAVs of Medicago truncatula were analyzed. Based on sequence data from the plant transcription factor database and the M. truncatula genome database, we cloned three RAV genes from M. truncatula, named MtRAV1, MtRAV2, and MtRAV3. The cis-acting elements of these genes promoters were predicted, and the expression patterns of MtRAVs under exogenous conditions (4°C, NaCl, Polyethylene Glycol, Abscisic acid) were analyzed. MtRAVs transgenic Arabidopsis thaliana were obtained and subjected to adversity treatment. Subcellular localization results indicated that MtRAVs were located in the nucleus. A much lower expression level was observed for MtRAV3 than the levels of MtRAV1 and MtRAV2 in M. truncatula for growth in normal conditions, but under 4°C or PEG and NaCl treatment, the expression level of MtRAV3 was significantly increased. Only the MtRAV3 overexpression transgenic plants showed strong cold resistance, but the overexpressed MtRAV1 and MtRAV2 transgenic plants showed no difference from wild type plants. MtRAV transgenic plants exhibited similar response to exogenous mannitol, NaCl, and ABA, and the expression of some adverse-related marker genes were up-regulated, such as COLD REGULATED 414 THYLAKOID MEMBRANE 1 (COR414-TM1), Arabidopsis thaliana drought-induced 21 (AtDI21), and Arabidopsis thaliana phosphatidylinositol-specific phospholipase C (ATPLC). MtRAVs transgenic Arabidopsis thaliana exhibited increasing of branch number. These results indicated that there was some function redundancy during MtRAVs proteins of M. truncatula, and MtRAV3 has increased function compared to the other two genes. The results of this study should provide the foundation for future application of MtRAVs in legumes.

Effect of exogenous spermidine on floral induction, endogenous polyamine and hormone production, and expression of related genes in 'Fuji' apple (Malus domestica Borkh.)

Flower bud formation in ‘Fuji’ apple (Malus domestica Borkh.) is difficult, which severely constrains commercial production. Spermidine (Spd) plays an important role in floral induction, but the mechanism of its action is incompletely understood. To investigate the effect of Spd on flowering, 6-year-old ‘Fuji’ apple trees were treated with 1 × 10⁻⁵ mol L⁻¹ Spd to study the responses of polyamines [putrescine (Put), Spd and spermine (Spm)], hormones [gibberellins (GA₃) and abscisic acid (ABA)], and polyamine-, hormone- and flowering-related genes. Spd application promoted flowering during floral induction by increasing MdGA2ox2 (gibberellin 2-oxidase) through GA₃ reduction and increasing MdNCED1 and MdNCED3 (9-cis-epoxycarotenoid dioxygenase) through ABA enrichment during 60 to 80 days after full bloom. The flowering rate as well as the expressions of flower-related genes, except for MdLEY (LEAFY), also increased, thereby promoting flowering. In addition, spraying with Spd significantly increased the contents of endogenous polyamines except for Spm in terminal buds by increasing the expressions of polyamine-associated genes. We hypothesize that the contribution of Spd to flowering is related to crosstalk among polyamines, hormone signals, and related gene expressions, which suggests that Spd participates in the apple floral induction process.