Application Of Larix Gmelinii UGPase Gene In Genetic Improvement Of 84K Poplar

Dahurian larch(Larix gmelinii)is the major tree species for afforestation in Greater Khingan Mountains area,which has dense material and strong mechanical properties and plays an important role in promoting economic development.As one of the key enzymes regulating plant polysaccharide metabolism,UDP-glucose pyrophosphorylase(UGPase)catalyzes the conversion of glucose-1-phosphate(G-1-P)and uridine triphosphate(UTP)to synthesize uridine diphosphate glucose(UDPG),a precursor substance for the synthesis of cellulose and callose,which is essential for the biosynthesis of plant cell walls.Therefore,UGPase plays a crucial role in the growth and development of plants and wood formation.Previous studies in our laboratory had confirmed that LgUGPase can promote the synthesis of cellulose and cell wall by regulating polysaccharide metabolism,thus the transgenic Arabidopsis overexpressing LgUGPase showed more growth advantages.Therefore,it is of great significance to further study expression characteristics of the LgUGPase gene and apply it to the genetic improvement of important forest trees.In this study,function and expression characteristics of the LgUGPases were conducted based on sequences of the LgUGPase1(named LgUGPase)and their promoters(named p LgUGPase1 and p LgUGPase2,respectively)cloned in our previous study,and genetic improvement of 84 K poplar(Populus alba × Populus glandulosa)was performed with the LgUGPase.The heterologous expression of the GUS reporter gene driven by LgUGPase promoters in the 84 K poplar showed that the expression of LgUGPase1 was induced by gibberellin(GA),abscisic acid(ABA),methyl jasmonate(Me JA)and low temperature(4 ℃);and the expression of LgUGPase2 was induced by mannitol(Mannitol),Me JA,GA and ethephon(Ethrel,ETH).Three transgenic 84 K poplar lines overexpressing LgUGPase were obtained by Agrobacterium-mediated transformation of leaf discss,and the growth and physiological indexes of the transgenic poplars were detected.The results showed that the transgenic lines had higher plant height,root length,root biomass,stem biomass,relative water content and chlorophyll content,comparing with non-transgenic plants(Non-transgenic,NT),which indicating that overexpression of LgUGPase gene promoted the vegetative growth of transgenic 84 K poplars.In order to explore the functional mechanism of that overexpression of LgUGPase gene promote the vegetative growth of 84 K poplar,the contents of fructose,glucose,sucrose,soluble sugar and starch in leaves,as well as the contents of cellulose,hemicellulose and lignin in stems of transgenic and non-transgenic plants cultivated for 30 days and 60 days in soil were detected.The results showed that overexpression of LgUGPase increased the contents of fructose,starch,cellulose and lignin in transgenic 84 K poplars,as well as the glucose content in transgenic lines cultivated in soil for 30 days.The above results show that the overexpression of the LgUGPase gene promotes the vegetative growth of transgenic 84 K poplars through regulation of carbohydrate metabolism,which provided theoretical and experimental basis for further analyzing of the functional mechanism and molecular regulation of LgUGPase gene,as well as its application in the genetic improvement of agricultural and forest trees.