Cui, Y. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Zhai, Y. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Flaishman, M. - Department of Fruit Tree Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
Li, J. - Fig Research Institute of Weiyuan County, Neijiang, Sichuan 642450, China
Chen, S. - College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, China
Zheng, C. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Ma, H. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China
Key message: The regulatory landscape of ethephon-accelerated fig ripening is revealed; flowers and receptacles exhibit opposite responses in anthocyanin accumulation; PG, PL and EXP are suggested key genes in fig softening. Abstract: Ethephon is used to accelerate fig-fruit ripening for improvement of harvesting efficiency, but the underlying molecular mechanism is still unclear. To elucidate the detailed biological mechanism of ethylene-accelerated fig ripening, fruit in phase II (the lag phase on the double sigmoid growth curve) were treated with ethephon, and reached commercial ripeness 6 days earlier than the nontreated controls. Transcriptomes of flowers and the surrounding receptacles—which together make up the pseudocarp in fig fruit—were analyzed. There were 5189, 5818 and 2563 differentially expressed genes (DEGs) 2, 4 and 6 days after treatment (DAT) in treated compared to control fruit, screened by p-adjust < 0.05 and |log2(fold change) |≥ 2. The DEGs were significantly enriched in plant hormone metabolism and signal transduction, cell-wall modification, sugar accumulation and anthocyanin accumulation pathways. DEGs in the first three pathway categories demonstrated an overall similar expression change in flowers and receptacles, whereas DEGs in anthocyanin pigmentation revealed divergent transcript abundance. Specifically, in both flowers and receptacles, ethephon significantly upregulated 1-aminocyclopropane-1-carboxylate oxidase and downregulated most of the ethylene-response factor genes; polygalacturonase, pectate lyase and expansin were mainly upregulated; two acid beta-fructofuranosidases were upregulated. However, structural genes in the anthocyanin-synthesis pathway were mainly downregulated in female flowers 2 and 4 DAT, whereas they were upregulated in the receptacles. Our study reveals the regulatory landscape of the two tissues of fig fruit in ethylene-induced ripening; the differentially expressed pathways and genes provide valuable resources for the mining of target genes for crucial biological and commercial trait improvement.
Cui, Y. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Zhai, Y. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Flaishman, M. - Department of Fruit Tree Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
Li, J. - Fig Research Institute of Weiyuan County, Neijiang, Sichuan 642450, China
Chen, S. - College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, China
Zheng, C. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China.
Ma, H. - Department of Fruit Tree Sciences, College of Horticulture, China Agricultural University, Beijing, 100193, China
Key message: The regulatory landscape of ethephon-accelerated fig ripening is revealed; flowers and receptacles exhibit opposite responses in anthocyanin accumulation; PG, PL and EXP are suggested key genes in fig softening. Abstract: Ethephon is used to accelerate fig-fruit ripening for improvement of harvesting efficiency, but the underlying molecular mechanism is still unclear. To elucidate the detailed biological mechanism of ethylene-accelerated fig ripening, fruit in phase II (the lag phase on the double sigmoid growth curve) were treated with ethephon, and reached commercial ripeness 6 days earlier than the nontreated controls. Transcriptomes of flowers and the surrounding receptacles—which together make up the pseudocarp in fig fruit—were analyzed. There were 5189, 5818 and 2563 differentially expressed genes (DEGs) 2, 4 and 6 days after treatment (DAT) in treated compared to control fruit, screened by p-adjust < 0.05 and |log2(fold change) |≥ 2. The DEGs were significantly enriched in plant hormone metabolism and signal transduction, cell-wall modification, sugar accumulation and anthocyanin accumulation pathways. DEGs in the first three pathway categories demonstrated an overall similar expression change in flowers and receptacles, whereas DEGs in anthocyanin pigmentation revealed divergent transcript abundance. Specifically, in both flowers and receptacles, ethephon significantly upregulated 1-aminocyclopropane-1-carboxylate oxidase and downregulated most of the ethylene-response factor genes; polygalacturonase, pectate lyase and expansin were mainly upregulated; two acid beta-fructofuranosidases were upregulated. However, structural genes in the anthocyanin-synthesis pathway were mainly downregulated in female flowers 2 and 4 DAT, whereas they were upregulated in the receptacles. Our study reveals the regulatory landscape of the two tissues of fig fruit in ethylene-induced ripening; the differentially expressed pathways and genes provide valuable resources for the mining of target genes for crucial biological and commercial trait improvement.