Mechanistic Study Of Variegated Leaf Formation In Arabidopsis Thaliana

Variegated-leaf plants are ideal materials for studying the mechanism of chloroplast development and interaction between plastid and nucleus,because of the coexistence of green sectors with normal chloroplast development and white or yellow sectors with abnormal chloroplast development in the same leaf.Although there are some hypotheses(such as threshold model and the balance between protein synthesis and degradation model)to explain the cause of leaf variegation formation,the detailed molecular mechanism is still unclear.The normal chloroplast division is very important for the growth of plants.However,to date,it is unclear whether chloroplast division is involved in the leaf variegation formation.In this study,we investigated the role of chloroplast division and cell division in leaf variegation formation of var2-1(yellow variegated 2-1)mutant in Arabidopsis.Chloroplast division was slowed down in var2-1,while cell division was normal.Cell division and chloroplast division are coordinated in the wild type with normal leave development,but in var2-1,chloroplast division was slowed down and was uncoordinated with cell division,resulting in cells containing undetectable plastids in the white sectors of var2-1 variegated leaves.Genetic analysis found that arc6-1 var2-1 and pdv1-1 var2-1 displayed more severe leaf variegation phenotypes and growth defects than var2-1,while overexpression of PDV1 and PDV2 can accelerate chloroplast division and partially rescue the leaf variegation of var2-1,which indicated that slowed chloroplast division can aggravate the leaf variegation of var2-1 and faster chloroplast division can alleviate the leaf variegation of var2-1.In addition,the variegation suppressors of var2-1,prpl11 and sot1,suppressed the formation of leaf variegation of var2-1 by accelerating chloroplast division.All the above results indicate that chloroplast division was involved in the leaf variegation formation of var2-1 in Arabidopsis thaliana.This process was related to uncoordinated chloroplast division and cell division,but more detailed molecular mechanism needs to be further studied.