Comprehensive Analysis Of SWEET Family In Eucalyptus(Eucalyptus Grandis)

SWEET family genescode theintegral membrane proteins that containtwo Mt N3/ saliva transmembrane domains from protozoa to eukaryotes.Currently, SWEET family genes are little known.Recent studies indicate the proteins coded by SWEET family genes may be used as a sugar transporter protein or by interaction with the ion transport proteins to promote ion transport. SWEET family genes play an important role in different physiological processes, includingthe transport of sugars adjustment, plant development,and the environmental adaptability.In this study, we used the bioinformatics method to analyze Eucalyptus SWEET family genes, including their evolution, their attributes and structure. The main findings are as follows:1. From Phytozome database, we retrieved Eucalyptus grandis and Arabidopsis thalianagenes containing the Mt N3/saliva domain. We observed 52 homologous sequences from Eucalyptus grandis and 17 homologous sequences from Arabidopsis thaliana.All 17 Arabidopsis sequences contain two Mt N3/saliva domains, and the numberof transmembrane domain is equal or greater than 6. All these homologous genes were defined as SWEET family.Amongthe 52 Eucalyptushomologous sequences,40 sequences have the number of transmembrane regionsof greater than or equal to 6,and contain two Mt N3 / saliva domains.These genes weredefined as SWEET family members. There are 6 sequences that have two Mt N3 / saliva domains, butthe number of their transmembrane domains is less than 6. These genes may be seen as SWEET family members. There are 6 sequences that have only one Mt N3 / saliva domain,similar to the structure of microbial Semi SWEETs. These sequences were not considered as SWEET family members.2. To study the evolution of the genes with Mt N3 / saliva domainsin different plants,we received a total of 947 genes from 37 different species.All of the 947 geneswere divided in phylogeny into 11 branches and some OG branches.We grouped these genes into A1, A2, A3 and B1 subfamilies. A1 subfamily included At SWEET4-8 and 6 Eucalyptus genes; A2 subfamily included At SWEET16, At SWEET17 and 6 Eucalyptus genes; A3 subfamily included At SWEET1-3 and 13 Eucalyptus genes;B1 subfamily included At SWEET9-15 and 24 Eucalyptus genes; and the rest parts of genes belonged to the OG branch.3. By searching for Phytozome databases and using DNAMAN software, we analyzed the basic properties of the Eucalyptus SWEET family genes. All of the 40 genes have the number of transmembrane regionsof greater than or equal to 6, and their open reading frames(ORF) range from 1208 bp to 7084 bp.Among other 12 genes,with the number oftransmembrane regions being less than 6, Eg SWEET2 d is the shortest, while Eg SWEET17 e is the longest. Theiropen reading frames rangefrom 529 bp to4615bp,and the number of exons ranges from 3 to 6.4. From the Phytozome database we mappedthe SWEETfamily genes on chromosomes.Only 45 genes are located on chromosomes. Eucalyptus has 11 chromosomes,andthe 45 SWEET family genes are distributed on 8 chromosomes.5. The expression experiment of the SWEET family genes was conducted with Eucalyptus.RNA was extracted from five tissues(shoot tips, young leaves, mature leaves, phloem and xylem).We found 34 genes with high levels of expressions in the shoot tips, 37 geneswith highexpression levels in the young leaves, 36 genes expressing in the mature leaves,31 genes with the highest level ofexpressions in the xylem,and 40 genes with high levels of expressions in the phloem.6. We found that under the treatment of glucose solution, expressions of 11 genes were up-regulated. Two genes expressions were down-regulated, and seven genes expressionswere unchanged. In the treatment of sucrose solution, 15 genes expression were up-regulated.Two genes expressions were down-regulated,and three genes expressions were unchanged.In the treatment of Na Cl solution, 11 genes were upregulated.Two genes expressions were down-regulated,and seven gene expressionswere unchanged. It was observed that most of these 20 genes were induced to express by the sucrose solution.These results help us to further understand the functions of the SWEETfamily genes in Eucalyptus.