SWEET1 Protein-coding Gene Is Involved In Pollen Germination And Stress Response In Picea Wilsonni

SWEETs sugar transporters are newly identified proteins widely distributed in prokaryotes and eukaryotes. Since SWEETs sugar transporters can uptake and efflux multiple sugars, they involves in many physiological processes in plants, which have important influence to development of plants, like plant-pathogen interaction and supply of carbohydrate in pollen developmental stages. While, studies on stresses of SWEETs sugar transporters were less and even almost no studies on characteristics of SWEETs transporters in Picea wilsonii were present. Here, a sugar transporter was isolated from cDNA library in Picea wilsonii, and we present a basic study. The results are as follows:1. This study have isolated a sugar transporter gene PwSWEET1, and the full length cDNA of PwSWEET1 is 1237 bp. The open reading frame has 286 bp encoding a protein with 261 amino acid residues. According to the analysis of multiple alignment and phylogenetic tree among PwSWEET1 and AtSWEETs, we identify that PwSWEET1 is most similar to AtSWEET4, AtSWEET5, AtSWEET6 and AtSWEET7.2. The tissue-specific expression patterns of indicate that PwSWEET1 has highest expression in pollen. Hormone and abiotic stresses responses imply that, PwSWEET1 is significantly enhanced under ABA treatment even to 15-folds. It shows different expression pattern under the treatments of cold and heat when upregulated by cold and downregulated by heat. The expression of PwSWEET1 is induced with treatments of drought and H2O2 and remains no drastic changes with MeJA and NaCl.3. Pollen germination assay shows that PwSWEET1 may involves in pollen germination and pollen tube growth; The expression of PwSWEET1 is induced when using 0.1% Ca2+ and 0.1%H3BO3 treat pollen, and we make a conjecture that it may participates in the pollen growth and development that in relation with B; The results of sugar specific of pollen in Picea wilsonii indicate that mannose is absolutely ineffective sugars and sucrose, maltose and glucose are effective sugars in which sucrose is the most effective; Analysis of expression of PwSWEET1 when exposed to different carbon sources in pollen imply that it is more likely to be induced by sucrose and glucose; Different factors that lead to abnormal in pollen shows that 0.1% Ca2+ can induce abnormal and also when the growth of pollen grains are not in optimal concentration of carbon sources.4. Heterologous functional analysis of sugar transporter PwSWEETl in yeast mutant indicate that it involves in transporting glucose, thus ensure the normal growth of yeast mutant on glucose medium. In addition, PwSWEET1 is not a pH-dependent sugar transporter.5. We have screened homologous T-DNA insertion mutants in Arabidopsis to the third generation.The overexpression vector of PwSWEETl and its homologous gene in Arabidopsis are constructed and the fusion plasmids are used to transformed into wild type and its corresponding mutants. Besides, we have constructed pollen-specific plasmid Lat52::PwSWEET1 to get a transient overexpression by gene gun.