Degradation Of Anthocyanin In Wucai Petioles Under Low Temperature Stress Mechanism Research

Brassica campestris L.ssp.chinensis var.rosularis Tsen(Brassica campestris L.ssp.chinensis var.rosularis Tsen)is a variety of cruciferous non-heading Chinese cabbage with abundant types and varieties.It is a winter vegetable product,which is mostly distributed in the Jianghuai River Basin and is popular with consumers.The petiole of Wucai parent W15-7-9-1 turned purple at low temperature,resulting in anthocyanin accumulation.After adapting to low temperature,anthocyanin degraded and petiole returned to white.At present,the degradation mechanism of anthocyanin in Wucai is still unclear.In this study,the color transformation of W15-7-9-1 petiole from purple to white was detected under low temperature conditions.The differential metabolites and differential genes were analyzed by metabolomics and transcriptomics to elucidate the molecular mechanism of anthocyanin degradation in Wucai petiole during low temperature stress.The main results are as follows :1.Observation of color difference and morphological characteristics of W15-7-9-1petiole during low temperature stressAt low temperature,the a* value(red-green value)increased significantly with the number of planting days(Day after planting,DAP).After reaching a certain limit,the petiole changed from purple to white,and the a* value decreased significantly with the number of planting days.At 3 DAP after planting,the petiole began to turn purple.At 32 DAP after planting,the petiole turned purple the deepest.At 36 DAP after planting,the petiole began to turn white from purple.At 60 DAP after planting,the petiole completely turned white.2.Detection of antioxidant capacity and injury degree of W15-7-9-1 petiole during low temperature stressIn the process of low temperature stress,the purple petiole(P)had lower malondialdehyde,superoxide anion and hydrogen peroxide content than the purple faded petiole(PF),which indicated that the PF was less damaged and more adapted to the low temperature environment,and then had stronger cold resistance,and the corresponding anthocyanin,peroxidase,catalase,superoxide dismutase content and total antioxidant capacity decreased.3.Metabolomics analysis of the effect of low temperature on the color change of petiole of WucaiMetabolomics data showed that the content of cyanidin was the highest in purple petiole(P),and the content of cyanidin in purple petiole(PF)was significantly reduced.The content of anthocyanin differential metabolite cyanidin-3,5,3 ’-O-triglucoside changed most significantly in P and PF,with the highest content in P and significantly decreased in PF.4.Transcriptome analysis of the effect of low temperature on the color change of petiole of WucaiUsing P and PF as materials,1914 differentially expressed genes were identified by comparative transcriptome analysis.Transcriptome results showed that plant-pathogen interaction,circadian rhythm,MAPK signal transduction and flavonoid biosynthesis pathway may be important ways to indirectly affect anthocyanin degradation.The up-regulation of WRKY25 / 29 transcription factor in plant-pathogen interaction and MAPK signaling pathway may activate the transcription of immune defense-related genes,and the up-regulation of LHY transcription factor in circadian rhythm pathway may improve plant tolerance to low temperature.These three transcription factors may indirectly regulate chalcone synthase(Bc CHS3)and cause anthocyanin degradation.