Transcriptome comparison analyses in UV-B induced AsA accumulation of Lactuca sativa L

BackgroundLettuce (Lactuca sativa L.) cultivated in facilities display low vitamin C (L-ascorbic acid (AsA)) contents which require augmentation. Although UV-B irradiation increases the accumulation of AsA in crops, processes underlying the biosynthesis as well as metabolism of AsA induced by UV-B in lettuce remain unclear.ResultsUV-B treatment increased the AsA content in lettuce, compared with that in the untreated control. UV-B treatment significantly increased AsA accumulation in a dose-dependent manner up until a certain dose.. Based on optimization experiments, three UV-B dose treatments, no UV-B (C), medium dose 7.2 KJ center dot m(- 2)center dot d(- 1) (U1), and high dose 12.96 KJ center dot m(- 2)center dot d(- 1) (U2), were selected for transcriptome sequencing (RNA-Seq) in this study. The results showed that C and U1 clustered in one category while U2 clustered in another, suggesting that the effect exerted on AsA by UV-B was dose dependent. MIOX gene in the myo-inositol pathway and APX gene in the recycling pathway in U2 were significantly different from the other two treatments, which was consistent with AsA changes seen in the three treatments, indicating that AsA accumulation caused by UV-B may be associated with these two genes in lettuce. UVR8 and HY5 were not significantly different expressed under UV-B irradiation, however, the genes involved in plant growth hormones and defence hormones significantly decreased and increased in U2, respectively, suggesting that high UV-B dose may regulate photomorphogenesis and response to stress via hormone regulatory pathways, although such regulation was independent of the UVR8 pathway.ConclusionsOur results demonstrated that studying the application of UV-B irradiation may enhance our understanding of the response of plant growth and AsA metabolism-related genes to UV-B stress, with particular reference to lettuce.

Automated summary

The study showed that UV-B irradiation can increase the vitamin C content in lettuce, but the processes underlying its biosynthesis and metabolism are unclear. Transcriptome sequencing revealed that the effect of UV-B on vitamin C is dose-dependent and associated with the MIOX gene in the myo-inositol pathway and the APX gene in the recycling pathway. High-dose UV-B may regulate photomorphogenesis and response to stress through hormone regulatory pathways. These findings enhance our understanding of the response of lettuce to UV-B stress and the metabolism-related genes of vitamin C.