Silencing of the phytoene desaturase (PDS) gene affects the expression of fruit-ripening genes in tomatoes.

BACKGROUND: Past research has shown that virus-induced phytoene desaturase (PDS) gene silencing via agroinjection in the attached and detached fruit of tomato plants results in a pale-yellow fruit phenotype. Although the PDS gene is often used as a marker for gene silencing in tomatoes, little is known about the role of PDS in fruit ripening. In this study, we investigated whether the pepper PDS gene silenced endogenous PDS genes in the fruit of two tomato cultivars, Dotaerang Plus and Legend Summer. RESULTS: We found that the pepper PDS gene successfully silenced endogenous PDS in tomato fruit at a silencing frequency of 100% for both cultivars. A pale-yellow silenced area was observed over virtually the entire surface of individual fruit due to the transcriptional reduction in phytoene desaturase (PDS), zeta-carotene (ZDS), prolycopene isomerase (CrtlSO), and beta-carotene hydroxylase (CrtR-b2), which are the carotenoid biosynthesis genes responsible for the red coloration in tomatoes. PDS silencing also affected the expression levels of the fruit-ripening genes Tomato AGAMOUS-LIKE1 (TAGL1), RIPENING INHIBITOR (RIN), pectin esterase gene (PE), lipoxygenase (LOX), FRUITFULL1/FRUITFUL2 (FUL1/FUL2), and the ethylene biosynthesis and response genes 1-aminocyclopropane-1-carboxylate oxidase 1 and 3 (ACO1 and ACO3) and ethylene-responsive genes (E4 and E8). CONCLUSION: These results suggest that PDS is a positive regulator of ripening in tomato fruit, which must be considered when using it as a marker for virus-induced gene silencing (VIGS) experiments in order to avoid fruit-ripening side effects.

Tomato seeds pretreated with Antifreeze protein type I (AFP I) promotes the germination under cold stress by regulating the genes involved in germination process.

This study was conducted to investigate the involvement of antifreeze proteins (AFPs; type I and III) in the germination mechanism of tomato seeds under low temperature stress. Germination of the seeds grown at a room temperature (25°C) was observed on 5 days after sowing (DAS), while all seeds exposed to a low temperature started to germinate at 16 days after sowing (DAS). However, in comparison with control seeds (0 µg/l), seeds treated with AFP I (100, 300, or 500 µg/l) germinated earlier and at a higher percentage until 20 DAS, and seeds treated with 100 µg/l AFP I showed the highest percentage of germination. Surprisingly, AFP III did not significantly increase germination, and the rate was lower among 500 µg/l AFP III-treated seeds compared with control seeds (0 µg/l). The transcription levels of the plasma membrane-associated H+-ATPase gene and antioxidant-related superoxide dismutase (SOD) and catalase 1 (CAT1) genes were analyzed, and the transcription levels of the genes in the seeds grown at 25°C were relatively low. For low temperature-treated seeds, H+-ATPase in control seeds (0 µg/l) was higher compared with that in AFP I-treated seeds and was lower compared with that in AFP III-treated seeds. The expression levels of the antioxidant-related genes (SOD and CAT1) were lower in AFP I-treated seeds than in control seeds (0 µg/l); however, they were higher in AFP III-treated seeds than in control seeds (0 µg/l). Overall, compared with AFP III, AFP I may potentially function as a cold-protective agent by modulating the genes associated with seed germination.

The role of antifreeze proteins in the regulation of genes involved in the response of Hosta capitata to cold.

Cold temperatures are a major source of stress for plants and negatively impact crop yield. A possible way to protect plants is to treat them with antifreeze proteins (AFPs). Here, we investigated whether fish AFPs can shield the rare ornamental species Hosta capitata from low-temperature stress. We elucidated the expression patterns of the cold-inducible genes C-repeat binding factor 1 (CBF1) and dehydrin 1 (DHN1), as well as the antioxidant genes superoxide dismutase (SOD) and catalase (CAT). All were upregulated at low temperature (4 °C). With increasing exposure time, CBF1 and DHN1 expression generally rose (except CBF1 at 48 h). In contrast, SOD and CAT expression gradually declined from 6 to 48 h. Depending on exposure duration, AFP regulation of gene transcription varied with concentration. However, compared with other concentrations, 100 µg/L AFP reduced CBF1 and DHN1 expression and increased SOD and CAT expression in plants, regardless of exposure time. Both AFP I and III were likely to be most effective at protecting plants against cold stress at concentrations of 100 µg/L. Their involvement in H. capitata cold-stress treatment occurred through regulating the expression of important stress-response genes.