The Relationship Between Anthocyanin Accumulation And Low Temperature Adaptability In Foxtail Millet

Anthocyanin,a derivative of 2-phenylbenzopyranyl,is abundant in plants.It has anti-oxidant,anti-bacterial and anti-cancer properties,and is also beneficial for vision and liver health.Previous researches show that the biosynthesis of anthocyanin can be enhanced by low temperature and it can induce stress resistance in plants.However,the reports about anthocyanins in foxtail millet are limited.The study of the mechanism on the induction of anthocyanidins by low temperature and its relationship with low temperature adaptability can lay a theoretical foundation for further researches on the anthocyanidins biosynthesis in foxtail millet.In this study,the purple and green leaf color varieties of foxtail millet were used as the research materials.In order to study the induction of anthocyanins by low temperature in foxtail millet,the phenotype and the total anthocyanin contents in leaves of the seedlings under low temperature treatment were analyzed.hurthermore,the contents of chlorophyll,soluble sugar,proline,malondialdehyde and other physiological indexes were compared between the purple and green leaf color varieties to determine the relationship between anthocyanins accumulation and the low temperature response ability in foxtail millet.Meanwhile,the relationship between the anthocyanin accumulation and low temperature environment adaptation of foxtail millet was also evaluated by the comparison of purple and green varieties leaf temperature and the distribution of purple leaf varieties under natural conditions.Finally,combining the transcriptional data of purple and green varieties and the bio-informatics analysis of the differential expressing genes related to anthocyanin,the correlation between the regulation of anthocyanins accumulation and low temperature induction was predicted.The main results are as follows:1.Low temperature could induce the accumulation of anthocyanins in the sheaths and leaves of purple variety,and it requires a certain induction time.On the contrary,the green leaves can not accumulate anthocyanins.Microscopic examination showed that anthocyanins were mainly distributed in the vacuoles of adaxial and abaxial face epidermis and adjacent mesophyll cell of foxtail millet leaves.2.The accumulation of soluble sugar and proline could be induced by low temperature stress in foxtail millet,and their contents were all significantly higher in purple leaf varieties than in green leaf varieties.This result indicates that the anthocyanin accumulation in foxtail millet might be related to the its adaptability to low temperature.3.The net photosynthetic rate and the relative content of chlorophyll in leaves of purple variety were significantly lower than the green leaf variety.Anthocyanins accumulation showed the negatively correlated to the net photosynthesis and the chlorophyll content.The relationship between anthocyanins and malondialdehyde in leaves of foxtail millet under low temperature stress needs to be further studied.4.The varieties of foxtail millet rich in anthocyanin are mainly from the cold climate areas of Northeast China,such as Hebei and Nei Mongol.The overall trend exhibited that the temperature of purple leaves were significantly higher than green leaves,while the electrical conductivity of purple leaves were significantly lower than green leaves.It indicated that anthocyanins could affect the adaption of foxtail millet to low temperature environment.5.Transcriptome analysis of purple and green leaf varieties showed low temperature stress-resistant genes related to sugar and fat metabolism,low temperature response genes,WRKY family,NAC family,C2H2 zinc finger structure transcription factors,and gibberellin genes were all significantly higher in purple leaves compared with green leaves,demonstrating that these genes were associated with the anthocyanin biosynthesis and the tolerance to low temperature stress.6.The analysis of the promoters of 15 genes related to the anthocyanin metabolic pathway revealed that some photoresponse MYB/yb,MYC/yc components,other adverse response components,low temperature response components i.e.DREc,DRE1,LTR,abscission acid,jasmonic acid,and gibberellin along with other important hormones for low-temperature signals were contained in promoter sequences.In conclusion,there were closely relationship between the regulation of anthocyanin biosynthesis and low temperature response in foxtail millet.