A New Insight into the Evolution and Functional Divergence of SWEET Transporters in Chinese White Pear (Pyrus bretschneideri)
A New Insight into the Evolution and Functional Divergence of SWEET Transporters in Chinese White Pear (Pyrus bretschneideri)
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对中国白梨 (Pyrus bretschneideri) 中甜转运蛋白的进化和功能分化的新见解
DOI：
10.1093/pcp/pcx025
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发表时间：
2017-04-01
影响因子：
4.9
通讯作者：
Wu, Jun
中科院分区：
文献类型：
--
作者：
Li, Jiaming;Qin, Mengfan;Wu, Jun
SWEET基因是最近发现的一个植物基因家族，在糖外排中起着不可或缺的作用。然而，尚未在梨中进行系统的研究。在这项研究中，梨中鉴定出18种SWEET转运蛋白，几乎是林地草莓和日本杏中发现的数量的两倍，分为四个分支。在6个物种中发现了保守的SWEET转运蛋白基序和6个外显子。SWEET转运蛋白含有7个跨膜片段（TMS），这些跨膜片段是从一个由TMS 4连接的祖先三TMS单元的内部复制进化而来的。这是第一个通过生物信息学分析确定内部重复序列的直接证据。全基因组重复（WGD）或片段重复和分散重复代表了SWEET家族在6个物种中进化的主要驱动力，前者的重复在梨中更重要。基因表达结果表明，PbSWEET 15和PbSWEET 17在任何组织中没有表达，因为关键的丢失残基和62.5%的PbSWEET重复基因对具有功能分歧。另外，PbSWEET 6、PbSWEET 7和PbSWEET 14在叶片蔗糖流出中起重要作用，PbSWEET 1和PbSWEET 2的高表达可能与茎中韧皮部蔗糖的卸载有关。PbSWEET 5、PbSWEET 9和PbSWEET 10可能参与花粉发育。总之，我们的研究为了解梨和其他四个蔷薇科植物中SWEET基因家族的进化提供了重要的信息，并在梨中鉴定了参与不同组织发育的重要候选基因PbSWEET。
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.