Effects Of UVR8 Gene On Fruit Shelf Life And Plant Disease Resistance In Tomato

Tomato is rich in nutrients,including vitamins,carotenoids and phenolic compounds,which has important economic and nutritional value.It is also an important model to study fruit development and formation of nutritional quality.UV resistance locus 8（UVR8）is the only known UV-B photoreceptor responsible for UV-B sensing and signal transduction.At present,the physiological functions of UVR8 in plants mainly focus on Arabidopsis,including inhibition of hypocotyl growth,epidermal stomatal enlargement,regulation of biological rhythm,improvement of photosynthetic rate and resistance to Botrytis cinerea.In this paper,the stable genetic homozygous overexpression genetic transformation tomato lines obtained in the previous research in the laboratory were used to study.Firstly,we investigated the effects of UVR8 overexpression and gene silencing on the nutritional quality and shelf life of tomato.The results showed that over expression of UVR8 could significantly prolong the shelf life of tomato fruit,and the firmness of fruit was significantly higher than that of wild type.The expression levels of 8 cellulase（Cel2 and Cel8）in fruit were significantly down regulated in UVR8 overexpression tomato,but up regulated in UVR8 gene silencing transgenic tomato,we speculate that UVR8 may participate in the hydrolysis of cell wall by regulating the expression of cellulase to prolong the storage of tomato fruit.In addition,the activities of catalase（CAT）and peroxidase（POD）in UVR8 transgenic tomato fruits were measured.We also found that the CAT and POD activities of UVR8overexpressing transgenic tomato fruits were significantly higher than those of wild type.However,in gene silencing,the fruit quality of tomato decreased significantly compared with that of wild type.At the same time,the content of malondialdehyde in the overexpressed tomato fruit decreased,only half of the wild type,and the MDA content of the tomato fruit with gene silence increased significantly compared with the wild type.The results suggest that UVR8 plays an important role in prolonging the shelf life of tomato fruit after harvest.We also studied the leaf phenotype,colony count,H₂O₂accumulation damage and trypan blue staining of UVR8 overexpression and gene silencing tomato plants inoculated with the pathogen Pseudomonas syringae pv.Tomato（Pst DC3000）and analyzed the effects of UVR8 overexpression and gene silencing on stress resistance of tomato strain Pst DC3000.The results showed that the number of Pst DC3000colonies and dead cells in the leaves of UVR8 overexpression tomato plants were significantly reduced compared with wild-type tomato plants.On the contrary,the number of leaf lesions,the number of colonies and dead cells of Pst DC3000 in UVR8gene silenced plants increased significantly,which indicated that overexpression of UVR8 gene enhanced the resistance of tomato plants to Pst DC3000,while UVR8gene silencing reduced the resistance of tomato plants to Pst DC3000.q RT-PCR showed that the expression level of resistance gene PR1a in UVR8-OE was significantly higher than that in wild-type,which also indicated that UVR8 might be involved in the regulation of disease resistance in tomato plants.Therefore,in this study,we found that UVR8 gene could significantly prolong the shelf life of tomato fruit,and transgenic had no significant adverse effects on fruit yield and quality characteristics.UVR8 gene played a positive regulatory role in tomato resistance to Pst DC3000,and could significantly improve the disease resistance of tomato plants.These results provide important theoretical basis for molecular breeding and genetic improvement of tomato.