Seasonal Variation Of Sucrose Metabolism-Related Enzyme Activity And Gene Expression In Latex And Bark Of Hevea Brasiliensis

In rubber tree,Sucrose is the major product of photosynthesis,and rubber biosynthesis needs sucrose to be the sole initial precursor molecule.Sucrose is the primary organic carbon that is synthesised in leaves,and translocated through phloem from photosynthetic leaves(source)into non-photosynthetic tissues(sink),including the rubber-producing laticifers latex.After phloem unloading in sinks,sucrose needs to be degraded into hexoses for latex regeneration and rubber production use by either invertase(Inv)that hydrolyses sucrose into glucose and fructose or sucrose synthase(Sus)that degrades sucrose into UDP-glucose and fructose.As the upstream of latex regeneration process,sucrose metabolism pathway in laticifers has been studied more,and bark as the most direct carbon pool for latex regeneration,but there are few studies on physiological parameters,enzyme activity and key gene expression in gum production related glucose metabolism pathway of latex and bark.In this paper,seasonal variation in activity of sucrose-metabolizing enzymes and expression of relevant genes in two carbon sinks(latex and trunk bark)that are directly involved in rubber production,as well as latex physiological parameters and bark n onstructural carbohydrate(NSC),were investigated in two Hevea varieties(Reyan7-33-97 and PR107)of differing rubber productivity.The main results are as follows:1.Besides,the rubber yield of rubber trees is affected not only by the variety difference,but also by the climatic conditions such as rainfall,temperature and humidity,and the influence of precipitation on the seasonal variation of latex yield of the two varieties is greater than that of the temperature,PR107 of which the influence is especially obvious.2.In most months,the yield and content of dry glue were higher than that of PR107,but the content of sucrose and inorganic phosphorus in latex were lower than PR107.Physiological parameters of latex were similar to the seasonal variation trend of NSC content in bark,and the two varieties had similar sugar metabolism ability in bark and latex.3.Methods of sucrose metabolism enzyme activities assay using crude enzyme had been a great improvement.The optimum activity of NIN、SSC、SSS in latex and NIN、VIN、SSC、SSS in bark was determined.4.Expression patterns of Hb SUT、Hb SWEET、Hb NIN、Hb SUS in latex and Hb NIN、Hb VIN、Hb CWI、Hb SUT、Hb SWEET、Hb SUS in bark had been analyzed.The results showed that there were significant differences in the expression patterns of most sucrose metabolism related genes between the two rubber trees.This study is the first systematic study of the physiological and biochemical parameters related to latex and bark production,sucrose metabolism related enzyme activities and the seasonal changes of key gene expression under the conditions of climate factors,rubber tree circumference,cutting,tapping technology and management level of rubber garden.