Physiological Basis Of Leaf Coloration And Transcriptomic Analysis For Anthocyanin Accumulation In North American Oak

Quercus species are widely distributed in the world.They are an important group of forest communities in the northern hemisphere,and have important ecological service functions and environmental protection values.In the past 20 years,the Institute of Subtropical Forestry of the Chinese Academy of Forestry has introduced more than 20 oak trees from the northeastern United States,including Quercus nattallii,Quercus shumardii,Quercus Phellos,etc.Autumn leaf color changes are abundant,and it has fast-growing and strong resistance to stress.It has become an important ecological landscape tree species in the Yangtze River Delta.However,many years of introduction experiments have found that the leaf color of North American oak tree varies greatly in different regions and even in the same region in different years.This study is based on the observation of the characteristics of the leaf color change of Quercus in different dimensions.The color difference parameters(L*,a*and b*)were used to evaluate leaf color characteristics of Quercus nattallii?Quercus shumardii?Quercus Phellos?Quercus lyrata?Quercus pagodifolia?Quercus michauxii?Quercus laurifolia and Quercus fabri 12 tree species and provenance leaves;by studying pigment content and C,N in autumn and winter in different regions,P,and carbohydrate supply dynamics,tracking nutrient transfer during leaf senescence and its effect on leaf color,and exploring the physiological basis of leaf color change in autumn and winter.By studying the leaf color changes of different provenances of Quercus nattallii under different site conditions in the same area,the influence of topographical conditions on the changes of leaf color was explored;by transcriptome sequencing of Q.nattallii with different color rendering characteristics of the leaves,the impact of key genes for anthocyanin accumulation in oak leaves.The main results are as follows:(1)At the regional scale,climatic factors have a significant impact on plant growth and leaf color changes.Generally speaking,humid,high temperature,and low wind speed areas(Anji area in this experiment)are suitable for the growth of oak trees.(2)Different site conditions and small changes in the ecological environment under the influence of slope did not significantly affect leaf color changes.In general,the leaf color parameter a~*value of flat field is larger than that of sloping field.The content of anthocyanins in the leaves of Q.fabri was lower than that of other tree species.This result is consistent with the regional test.(3)Through correlation analysis,it was found that there was a strong correlation between the leaf color parameter a~*and pigments,leaf elements and other indicators,which could be used as the main indicator for evaluating the leaf color change of Q.nattallii.Principal component analysis found that chlorophyll,anthocyanins,soluble sugars,and N and P in the leaves were the main substances that affected the changes in the leaves of Quercus.The reason for the significant difference in leaf color change of different provenances is due to its high genetic diversity.Site conditions have little effect on different provenances.The leaf color changes were more obvious in LA and TX provenances,while the less significant changes were in MS and AR provenances.(4)The phenotype separation of red and green leaves of Q.nattallii appears to be related to the accumulation of anthocyanins in Q.nattallii.Through transcriptome sequencing,a total of1395 differential genes were detected,of which 9 structural genes covered.The main steps of the anthocyanin pathway include chalcone synthase,chalcone isomerase,flavanone 3-hydroxylase,dihydroflavonol 4-reductase,and anthocyanin synthase.At the same time,9MYBs,1 bHLH and 1 WD40 genes,which are considered to be anthocyanin accumulation regulating genes,were identified,all of which were up-regulated.Therefore,it is inferred that the leaf color variation of Q.nattallii is an abnormal anthocyanin synthesis,and this result needs further research and verification.In general,the TX provenance of Q.nattallii,Q.Phellos and Q.pagodifolia have significant changes in leaf color in autumn and winter,which is suitable for planting in southern China.If it is necessary to maintain the evergreen landscape pattern,it is recommended to plant Q.laurifolia.It is not recommended to plant AR provenances of Q.nattallii and Q.michauxii,because the leaves fall off more seriously in autumn and winter.