A New Insight into the Evolution and Functional Divergence of SWEET Transporters in Chinese White Pear (Pyrus bretschneideri).
SWEET genes are a recently identified plant gene family that play an indispensable role in sugar efflux. However, no systematic study has been performed in pear. In this research, 18 SWEET transporters identified in pear, almost twice the number found in woodland strawberry and Japanese apricot, were divided into four clades. Conserved motifs and six exons of the SWEET transporters were found in six species. SWEET transporters contained seven transmembrane segments (TMSs) that evolved from an internal duplication of an ancestral three-TMSs unit, connected by TMS4. This is the first direct evidence identifying internal repeats through bioinformatics analysis. Whole-genome duplication (WGD) or segmental duplication and dispersed duplication represent the main driving forces for SWEET family evolution in six species, with former duplications more important in pear. Gene expression results suggested that PbSWEET15 and PbSWEET17 have no expression in any tissues because of critical lost residues and that 62.5% of PbSWEET duplicate gene pairs have functional divergence. Additionally, PbSWEET6, PbSWEET7 and PbSWEET14 were found to play important roles in sucrose efflux from leaves, and the high expression of PbSWEET1 and PbSWEET2 might contribute to unloading sucrose from the phloem in the stem. Finally, PbSWEET5, PbSWEET9 and PbSWEET10 might contribute to pollen development. Overall, our study provides important insights into the evolution of the SWEET gene family in pear and four other Rosaceae, and the important candidate PbSWEET genes involved in the development of different tissues were identified in pear.
Institute of Applied Ecology, Chinese Academy of Sciences, Shenhe District, Shenyang, Liaoning, China.
Jiaming
J
Li
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Agronomy, Northwest A&F UniversityYangling, China.
Mengfan
M
Qin
Centre of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China.
Xin
X
Qiao
Key laboratory of Biology and Genetic Improvement of Oil Crops, Ministry of Agriculture, Oil Crops Research Institute, Chinese Academy of Agricultural Science, Wuhan, China.
Yinsheng
Y
Cheng
Laboratory of Fruit Quality Biology, Zhejiang University, Zijingang Campus, Hangzhou, China.
Xiaolong
X
Li
Henan Sesame Research Center, Henan Academy of Agricultural SciencesZhengzhou, China.|Henan Provincial Key Laboratory for Oil Crops ImprovementZhengzhou, China.
Huping
H
Zhang
Key Laboratory of Soybean Cultivation of Ministry of Agriculture China, Soybean Research Institute, Heilongjiang Academy of Agricultural SciencesHarbin, China.
Jun
J
Wu
D002462:Cell Membrane / Q000378:metabolism; D019143:Evolution, Molecular; D005091:Exons; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D007438:Introns; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D031989:Pyrus / Q000235:genetics* / Q000378:metabolism
D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins
Chinese white pear (Pyrus bretschneideri Rehd); Divergence time; Duplication modes; Internal repeat; SWEET transporter; qRT-PCR