Supplementary Red Light Results In The Earlier Ripening Of Tomato Fruit Depending On Ethylene Production

In greenhouse tomato production,the lower canopy of tomato plants is often shaded by the neighbouring tomato plants,and it is often cloudy or rainy during winter or spring in south China.Low light environment affects the yield and quality in greenhouse crop production.Supplementary lighting can be used to provide sufficient light energy for plants.Red light is regarded as the most efficient spectrum in supplementary lighting.Whether and how supplementary red light in the ambient of sunlight affect the ripening of tomato remain to be elucidated.In this research,the impacts of supplementary red light on tomato ripening were examined by comparing the impacts of supplementary red light on ripening-related regulators,ethylene synthesis,ethylene signaling,carotenoid synthesis and light signaling in Micro-Tom wild type tomato fruit and ripening-inhibitor(rin)mutant.The main results are as follows:1.Supplementary red light accelerated the color transition of wild type(WT)tomato,approximately 3 days in advance compared to control.But supplementary red light could not make the fruit of rin mutant change into red.2.Supplementary red light improved the expression of Sl RIN in WT tomato fruit,which induced the expressions of other ripening-related regulators,such as TAGL1,CNR and NOR.Then the expressions of Sl ACS2 and Sl ACS4 were initiated,ripening-related ethylene was produced,so the fruit of WT tomato showed earlier ripening than control.However,the influence of supplementary red light in ethylene transduction pathway was not obvious.In rin mutant,deficiency of Sl RIN decreased the expressions of other ripening-related regulators,which inhibited the production of ripening-related ethylene.But the deficiency of Sl RIN did not affect the ethylene transduction pathway.3.Supplementary red light promoted the expression of Sl GGPPS,which improved the accumulation of GGPP in WT tomato fruit.Besides,supplementary red light improved the accumulation of active phytochromes in WT tomato fruit,which induced the expression of Sl PSY1,therefore more phytoene was accumulated in WT tomato fruit.In rin mutant,deficiency of Sl RIN did not inhibit the expressions of all genes in carotenoid biosynthesis pathway except Sl PSY1,the rate-limiting gene in carotenoid biosynthesis pathway,so the fruit of rin mutant could not produce phytoene and the color of the fruit was green.In conclusion,supplementary red light promoted the expression of Sl RIN,improved the accumulation of active phytochromes and increased the production of ripening-related ethylene,therefore supplementary red light resulted in the earlier ripening of WT tomato fruit and increased the content of phytoene in WT tomato fruit.