Acyl-CoA synthetase 1 plays an important role on pollen development and male fertility in tomato.

The development of pollen is critical to male reproduction in flowering plants. Acyl-CoA synthetase (ACOS) genes play conserved functions in regulating pollen development in various plants. Our previous work found that knockout of the SlACOS1 gene in tomato might decrease fruit setting. The current study further revealed that SlACOS1 was important to pollen development and male fertility. The SlACOS1 gene was preferentially expressed in the stamen of the flower with the highest expression at the tetrad stage of anther development. Mutation of the SlACOS1 gene by the CRISPR/Cas9-editing system reduced pollen number and viability as well as fruit setting. The tapetum layer exhibited premature degradation and the pollen showed abnormal development appearing irregular, shriveled, or anucleate in Slacos1 mutants at the tetrad stage. The fatty acid metabolism in anthers was significantly impacted by mutation of the SlACOS1 gene. Furthermore, targeted fatty acids profiling using GC-MS found that contents of most fatty acids except C18:1 and C18:2 were reduced. Yeast complementation assay demonstrated that the substrate preferences of SlACOS1 were C16:0 and C18:0 fatty acids. Male fertility of Slacos1 mutant could be slightly restored by applying exogenous palmitic acid, a type of C16:0 fatty acid. Taken together, SlACOS1 played important roles on pollen development and male fertility by regulating the fatty acid metabolism and the development of tapetum and tetrad. Our findings will facilitate unraveling the mechanism of pollen development and male fertility in tomato.

Transcription factor FvTCP9 promotes strawberry fruit ripening by regulating the biosynthesis of abscisic acid and anthocyanins.

The plant-specific transcription factor TEOSINTE BRANCHED 1, CYCLOIDEA, and PROLIFERATING4 CELL FACTORS (TCP) plays a crucial role in plant growth and development. However, there have been no studies reporting on the function of strawberry TCP in regulating fruit development. In this study, FvTCP9, a woodland strawberry (Fragaria vesca) TCP gene, was isolated to explore its function in fruit ripening. The transcript accumulation levels of FvTCP9 were high in fruits, specifically in red fruits compared with other tissues or organs. Transient expression of the FvTCP9 gene in cultivated strawberry fruits revealed that over-expression of FvTCP9 promoted fruit ripening. Meanwhile, silencing FvTCP9, using tobacco rattle virus-induced gene silencing (VIGS), inhibited fruit ripening. The changes in ripening-related physiological conditions in transient fruits, such as the accumulation of anthocyanins and abscisic acid (ABA), and fruit firmness confirmed above results. Results suggested that FvTCP9 was involved in the biosynthesis of ABA and anthocyanins to regulate fruit ripening. Transcription analysis showed that the expression levels of ABA signaling-related genes (FaNCED1, FaPYR1, FaSnRK2, and FaABI5) were affected by FvTCP9. A yeast two-hybrid assay revealed that FvTCP9 interacted physically with FaMYC1 to modulate the biosynthesis process of anthocyanins. Taken together, this study demonstrated that FvTCP9 promoted fruit ripening by regulating the biosynthesis of ABA and anthocyanins.

Ectopic expression of FvWRKY42, a WRKY transcription factor from the diploid woodland strawberry (Fragaria vesca), enhances resistance to powdery mildew, improves osmotic stress resistance, and increases abscisic acid sensitivity in Arabidopsis.

WRKY transcription factors play a critical role in biotic and abiotic stress responses in plants, but very few WRKYs have been reported in strawberry plants. Here, a multiple stress-inducible gene, FvWRKY42, was isolated from the wild diploid woodland strawberry (accession Heilongjiang-3). FvWRKY42 expression was induced by treatment with powdery mildew, salt, drought, salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA), and ethylene. The protein interaction network analysis showed that the FvWRKY42 protein interacts with various stress-related proteins. Overexpression of FvWRKY42 in Arabidopsis resulted in cell death, sporulation, slow hypha growth, and enhanced resistance to powdery mildew that was concomitant with increased expression of PR1 genes in Arabidopsis. Overexpression also led to enhanced salt and drought stress tolerance, increased primary root length and germination rate, decreased water loss rate, reduced relative electrolyte leakage, and malondialdehyde accumulation, and upregulation of superoxide dismutase and catalase activity. Additionally, FvWRKY42-overexpressing Arabidopsis plants showed increased ABA sensitivity during seed germination and seedling growth, increased stomatal closure after ABA and drought treatment, and altered expression of ABA-responsive genes. Collectively, our data demonstrate that FvWRKY42 may play an important role in powdery mildew infection and the regulation of salt and drought stress responses in plants.