Polysaccharides are major bioactive ingredients in the medicinal tubers of Bletilla striata (Thunb.) Rchb.f. The SWEET (Sugars Will Eventually Be Exported Transporters) family is widely identified as bidirectional transporters mediating sugar translocation between source and sink tissues in plants. However, to date, SWEET family members have not been reported in B. striata, as well as the roles in sugar transport and B. striata polysaccharide (BSP) accumulation have not been elucidated. Here, by combining multiple RNA-seq datasets, a de novo transcriptome was assembled to identify SWEET genes in B. striata. Seventeen BsSWEETs were found, which were phylogenetically divided into four clades. Most BsSWEETs contain seven transmembrane domains (TMs) composed of two MtN3/saliva domains. Four of the seven TMs were conserved in the B. striata SWEET family. The expression profiles showed that BsSWEET1, 2b and 3a were the most dominant in tubers, leaves, and roots, respectively. Additionally, BsSWEET4, 5, 11 and 12 responded to exogenous MeJA. According to the co-expression pattern and interaction network prediction, BsSWEET2a-BsSWEET2b, BsSWEET4-BsSWEET5, and BsSWEET11-BsSWEET12 pairs were potential dimers formed during functioning. Furthermore, Bst-miR396g/h and a number of long non-coding RNAs (lncRNAs) were predicted to be involved in BsSWEETs regulation. In particularly, based on sequence alignment and qRT-PCR analysis, lncRNA MSTRG.63923 was likely to act as a competitive endogenous RNA (ceRNA) to compete with BsSWEET1 for Bst-miR396g/h. In conclusion, this study, provides comprehensive information about BsSWEETs and is beneficial for further functional analysis of the SWEET family in B. striata.

多糖是白芨(Thunb.) Rchb.f药用块茎中的主要生物活性成分。SWEET（糖最终将被输出转运蛋白）家族被广泛认为是介导植物中源组织和库组织之间糖易位的双向转运蛋白。然而，迄今为止，尚未报道B. striata中的 SWEET 家族成员，以及在糖转运和B. striata多糖 (BSP) 积累中的作用尚未阐明。在这里，通过结合多个 RNA-seq 数据集，组装了一个从头转录组来识别B. striata中的SWEET基因。十七个BsSWEET被发现，它们在系统发育上分为四个进化枝。大多数BsSWEET包含七个跨膜结构域 (TM)，由两个 MtN3/唾液结构域组成。七个 TM 中的四个保存在B. striata SWEET 家族中。表达谱显示BsSWEET1、2b和3a分别在块茎、叶和根中最显着。此外，BsSWEET4、5、11和12对外源性MeJA有反应。根据共表达模式和交互网络预测，BsSWEET2a - BsSWEET2b , BsSWEET4 -BsSWEET5和BsSWEET11 - BsSWEET12对是在功能过程中形成的潜在二聚体。此外，预测 Bst-miR396g/h 和许多长链非编码 RNA (lncRNA) 参与BsSWEET调控。特别是，基于序列比对和 qRT-PCR 分析，lncRNA MSTRG.63923可能作为竞争性内源 RNA (ceRNA) 与BsSWEET1竞争Bst-miR396g/h。总之，本研究提供了有关BsSWEET 的全面信息，有利于对B. striata中 SWEET 家族的进一步功能分析。