Function Study Of Cell Wall Invertase On Carbon Partitioning And Growth In Cassava(Manihot Esculenta)

CWINs(cell wall invertases)play pivotal roles in the distribution and regulation of plant photoassimilates have been confirmed in a variety of plant species such as Arabidopsis,rice,and tomato.This study aimed to investigate the roles of CWINs in the sugar metabolisms of root crop cassava especially the influence on the source-to-sink translocation and leaf senescence.MeCWINV3,as the highest expressing CWIN in cassava leaves,which showed significant changes during the development of cassava,was chosen as target gene.A MeCWINV3 overexpression vector was constructed and transformed into cassava to get transgenic plants.The physiological and biochemical indexes of the transgenic plants were studied,moreover RNA-seqs were conducted to analyze differentially expressed genes.The main results are as follows:Overexpression of MeCWINV3 increased the activity of cell wall invertase in both leaves and roots,and resulted in a decrease of sucrose content and a increase of glucose and fructose content in leaves.The stable isotope experiments showed that the content of sucrose was significantly decreased,which indicated the decrease of solute sugars content may be the main reason of root development inhibition.The detection result of transience starch in leaves showed that the transience starch of OE plants haven,t been consumed out during the dark period,which was presumed to be related to the down-regulation of GWD,a key gene for starch degradation.Compared with the wild type,the senescence of OE-MeCWINV3 plants leaves was accelerated.By the RNA-seq technology,the results showed that ABA signal pathway related genes were changed dynamically.It is presumed that OE-MeCWINV3 caused the changes of sugar homeostasis,which contributes to the genes changes within ABA signaling pathway,and thus cause the up-regulation of ROS and PCD,which may be associated with plants senescence.In conclusion,MeCWINV3 plays important role in photoassimilate distribution between source and sink.OE-MeCWINV3 may lead the sucrose decrease in source,resulting in a decrease in the photosynthate transported outward,and a decrease in the yield of storage root.MeCWINV3 can catalyze sucrose to form monosaccharides,which caused expression changes of ABA signaling pathway related genes,causing plant senescence.This study is of great significance to elaborate the mechanisms of photoassimilate distribution regulated by the cell wal invertase and the plant senescence caused by sugar homeostasis,which also associated with MeCWINV3 activities.All the results will provide a theoretical basis for the improvement of cassava breeding.