Functional Analysis Of Sucrose Transporter Genes OsSWEET11 And OsSWEET14 In Rice

Sucrose is the main sugar form for long distance transport in higher plants,it is the major substance for "sink" organ growth and development.As a result,sucrose transport between tissues and cells are important processes need to be addressed.Two families of sugar transporters,SUT(C)and SWEET,are identified to involved in these precesses based on present research.They assume sucrose influx from apoplast and efflux from cytosol,respectively.Research in Arabidopsis revealed that SWEET proteins play important roles in interaction between plant and microbial pathogen,or stress induced reactions,particularly in seed or fruit development based on their sugar transport ability,demonstrating that they are important factional proteins.In rice,a total of 21 putative SWEET members are predicted,but only a few have been characterized so far.Rice gene expression chip showed that as homologs of AtSWEETll,sucrose transporter OsSWEET11 and OsSWEET14 expressed strongly in rice developing caryopsis,impling that they may have important function in this process.We thus select these two genes as target genes and our findings including:1.qRT-PCR showed that both OsSWEETll and OsSWEET14 were expressed in rice roots,culm,leaf and flower.Particularly,OsSWEET11expressed very strongly in developing caryopsis.2.GUS labelled expression under the genes native promoters indicate that consistent with the qRT-PCR results,OsSWEET11 was expressed strongly in ovular vascular and nucellus epidermis of developing caropsis.sSWEET14 has similar expressional pattern but was expressed much weaker in caryopsis.In addition,they were both expressed in primordium of rice adventitious roots.Transient expression in tabacco epidermis of them showed that they localized at plasmmembrane.3.Knockout rice lines of OsSWEETll displayed inadequacy of seed-filling,lighter seed weight and decrease of setting percentage.By contrast,knockout lines of OsSWEET14 did not bring obvious phenotype in rice caryopsis,but development of adventicious roots was affected to some extent.In conclusion,our preliminary research showed that OsSWEET11 plays indispensable and important role in rice caryopsis development,while OsSWEET14 exerts its effect on rice adventitious root growth.Combined with detailed examination of the mutant’s physiological phenotypes in the next step,our research are hopefully clarify the mechanism of phloem unloading in ovular vascular during caryopsis development and expand our understanding in rice root growth.