CmDOF18 positively regulates salinity tolerance in Chrysanthemum morifolium by activating the oxidoreductase system

BACKGROUND

Chrysanthemum, one of the four major cut flowers all over the world, is very sensitive to salinity during cultivation. DNA binding with one finger (DOF) transcription factors play important roles in biological processes in plants. The response mechanism of CmDOF18 from chrysanthemum to salt stress remains unclear.

RESULTS

In this study, CmDOF18 was cloned from Chrysanthemum morifolium, and its expression was induced by salinity stress. The gene encodes a 291-amino acid protein with a typical DOF domain. CmDOF18 was localized to the nucleus in onion epidermal cells and showed transcriptional activation in yeast. CmDOF18 transgenic plants were generated to identify the role of this gene in resistance to salinity treatment. Chrysanthemum plants overexpressing CmDOF18 were more resistant to salinity stress than wild-type plants. Under salinity stress, the malondialdehyde content and leaf electrolyte conductivity in CmDOF18-overexpressing transgenic plants were lower than those in wild-type plants, while the proline content, chlorophyll content, superoxide dismutase activity and peroxidase activity were higher than those in wild-type plants. The opposite findings were observed in gene-silenced plants compared with wild-type plants. The gene expression levels of oxidoreductase increased in CmDOF18-overexpressing transgenic plants but decreased in CmDOF18-SRDX gene-silenced transgenic plants.

CONCLUSION

In summary, we analyzed the function of CmDOF18 from chrysanthemum, which may regulate salinity stress in plants, possibly due to its role in the regulation of oxidoreductase.

Transcriptomic and Physiological Response of Durum Wheat Grain to Short-Term Heat Stress during Early Grain Filling

In a changing climate, extreme weather events such as heatwaves will be more frequent and could affect grain weight and the quality of crops such as wheat, one of the most significant crops in terms of global food security. In this work, we characterized the response of Triticum turgidum L. spp. durum wheat to short-term heat stress (HS) treatment at transcriptomic and physiological levels during early grain filling in glasshouse experiments. We found a significant reduction in grain weight (23.9%) and grain dimensions from HS treatment. Grain quality was also affected, showing a decrease in starch content (20.8%), in addition to increments in grain protein levels (14.6%), with respect to the control condition. Moreover, RNA-seq analysis of durum wheat grains allowed us to identify 1590 differentially expressed genes related to photosynthesis, response to heat, and carbohydrate metabolic process. A gene regulatory network analysis of HS-responsive genes uncovered novel transcription factors (TFs) controlling the expression of genes involved in abiotic stress response and grain quality, such as a member of the DOF family predicted to regulate glycogen and starch biosynthetic processes in response to HS in grains. In summary, our results provide new insights into the extensive transcriptome reprogramming that occurs during short-term HS in durum wheat grains.

Transcription factor CDF4 promotes leaf senescence and floral organ abscission by regulating abscisic acid and reactive oxygen species pathways in Arabidopsis

Leaf senescence is a highly complex developmental process that is tightly controlled by multiple layers of regulation. Abscisic acid (ABA) and reactive oxygen species (ROS) are two well-known factors that promote leaf senescence. We show here that the transcription factor CDF4 positively regulates leaf senescence. Constitutive and inducible overexpression of CDF4 accelerates leaf senescence, while knockdown of CDF4 delays it. CDF4 increases endogenous ABA levels by upregulating the transcription of the ABA biosynthesis genes 9-cis-epoxycarotenoid dioxygenase 2, 3 (NCED2, 3) and suppresses H₂ O₂ scavenging by repressing expression of the catalase2 (CAT2) gene. NCED2, 3 knockout and CAT2 overexpression partially rescue premature leaf senescence caused by CDF4 overexpression. We also show that CDF4 promotes floral organ abscission by activating the polygalacturonase PGAZAT gene. Based on these results, we propose that the levels of CDF4, ABA, and ROS undergo a gradual increase driven by their interlinking positive feedback loops during the leaf senescence and floral organ abscission processes.

Rice OsDOF15 contributes to ethylene-inhibited primary root elongation under salt stress

In early seedlings, the primary root adapts rapidly to environmental changes through the modulation of endogenous hormone levels. The phytohormone ethylene inhibits primary root elongation, but the underlying molecular mechanism of how ethylene-reduced root growth is modulated in environmental changes remains poorly understood. Here, we show that a novel rice (Oryza sativa) DOF transcription factor OsDOF15 positively regulates primary root elongation by regulating cell proliferation in the root meristem, via restricting ethylene biosynthesis. Loss-of-function of OsDOF15 impaired primary root elongation and cell proliferation in the root meristem, whereas OsDOF15 overexpression enhanced these processes, indicating that OsDOF15 is a key regulator of primary root elongation. This regulation involves the direct interaction of OsDOF15 with the promoter of OsACS1, resulting in the repression of ethylene biosynthesis. The control of ethylene biosynthesis by OsDOF15 in turn regulates cell proliferation in the root meristem. OsDOF15 transcription is repressed by salt stress, and OsDOF15-mediated ethylene biosynthesis plays a role in inhibition of primary root elongation by salt stress. Thus, our data reveal how the ethylene-inhibited primary root elongation is finely controlled by OsDOF15 in response to environmental signal, a novel mechanism of plants responding to salt stress and transmitting the information to ethylene biosynthesis to restrict root elongation.

Understanding the functions of endogenous DOF transcript factor in Chlamydomonas reinhardtii

BACKGROUND

The regulation of genes related to lipid metabolism by genetic engineering is an important way to increase the accumulation of lipids in microalgae. DNA binding with one finger (DOF) is a plant-specific transcription factor in higher plants, where it regulates carbon and nitrogen metabolic pathways by regulating key genes involved in these pathways. Overexpression of DOF can increase lipid production in plants; however, it is not clear whether overexpression of DOF can increase lipids in microalgae.

RESULTS

In this study, we cloned a DOF transcription factor, crDOF, from Chlamydomonas reinhardtii. The sequence of this transcription factor is 1875 bp and encodes a peptide of 624 amino acids with a conserved DOF domain. Overexpression of crDOF in C. reinhardtii significantly increased the intracellular lipid content. The content of total fatty acids in the transgenic algae line Tran^c-crDOF-12 was 126.01 μg/mg (dry weight), which was 23.24% higher than that of the wild type. Additionally, the content of unsaturated fatty acids in the transgenic Tran^c-crDOF-12 line increased significantly. Fluorescence quantitative PCR analysis showed that in the transgenic line Tran^c-crDOF-12, the expression levels of BCC1, FAT1, SQD1, MGD1, DGD1 and PGP1 genes were significantly upregulated, while the expression levels of ACP1, ACS1, CIS1 and SQD2 were downregulated.

CONCLUSIONS

Our results confirm that crDOF increases intracellular lipids in C. reinhardtii by regulating key genes involved in lipid metabolism. According to these findings, we propose that enhancing the lipid content in microalgae by overexpressing DOF may be achieved in other industrial strains of microalgae and be employed for the industrial production of biodiesel.

The fruit-specific transcription factor FaDOF2 regulates the production of eugenol in ripe fruit receptacles

Only a few transcription factors have been described in the regulation of the strawberry (Fragaria x ananassa) fruit ripening process. Using a transcriptomic approach, we identified and functionally characterized FaDOF2, a DOF-type ripening-related transcription factor, which is hormonally regulated and specific to the receptacle, though high expression levels were also found in petals. The expression pattern of FaDOF2 correlated with eugenol content, a phenylpropanoid volatile, in both fruit receptacles and petals. When FaDOF2 expression was silenced in ripe strawberry receptacles, the expression of FaEOBII and FaEGS2, two key genes involved in eugenol production, were down-regulated. These fruits showed a concomitant decrease in eugenol content, which confirmed that FaDOF2 is a transcription factor that is involved in eugenol production in ripe fruit receptacles. By using the yeast two-hybrid system and bimolecular fluorescence complementation, we demonstrated that FaDOF2 interacts with FaEOBII, a previously reported regulator of eugenol production, which determines fine-tuning of the expression of key genes that are involved in eugenol production. These results provide evidence that FaDOF2 plays a subsidiary regulatory role with FaEOBII in the expression of genes encoding enzymes that control eugenol production. Taken together, our results provide new insights into the regulation of the volatile phenylpropanoid pathway in ripe strawberry receptacles.

Transcriptional control of strawberry ripening - two to tango

This article comments on: Molina-Hidalgo FJ, Medina-Puche L, Cañete-Gomez CJ, et al. 2017. The fruit-specific transcription factor FaDOF2 regulates the production of eugenol in ripe fruit receptacles. Journal of Experimental Botany 68, 4529–4543.