Laboratory of Cell and Molecular Biology, Institute of Vegetable Science, Zhejiang University, 866 Yuhangtang Road, Zhejiang Province, Hangzhou, 310058, P. R. China.
Laboratory of Horticultural Plant Growth and Quality Regulation, Ministry of Agriculture, Zhejiang Province, Hangzhou, 310058, P. R. China.
BMC Genomics. 2018 Mar 2;19(1):174. doi: 10.1186/s12864-018-4554-8.
Members of the MtN3/saliva/SWEET gene family are present in various organisms and are highly conserved. Their precise biochemical functions remain unclear, especially in Chinese cabbage. Based on the whole genome sequence, this study aims to identify the MtN3/saliva/SWEETs family members in Chinese cabbage and to analyze their classification, gene structure, chromosome distribution, phylogenetic relationship, expression pattern, and biological functions.
We identified 34 SWEET genes in Chinese cabbage and analyzed their localization on chromosomes and transmembrane regions of their corresponding proteins. Analysis of a phylogenetic tree indicated that there were at least 17 supposed ancestor genes before the separation in Brassica rapa and Arabidopsis. The expression patterns of these genes in different tissues and flower developmental stages of Chinese cabbage showed that they are mainly involved in reproductive development. The Ka/Ks ratio between paralogous SWEET gene pairs of B. rapa were far less than 1. In our previous study, At2g39060 homologous gene Bra000116 (BraSWEET9, also named BcNS, Brassica Nectary and Stamen) played an important role during flower development in Chinese cabbage. Instantaneous expression experiments in onion epidermal cells showed that the gene encoding this protein is localized to the plasma membrane. A basal nectary split is the phenotype of transgenic plants transformed with the antisense expression vector.
This study is the first to perform a sequence analysis, structures analysis, physiological and biochemical characteristics analysis of the MtN3/saliva/SWEETs gene in Chinese cabbage and to verify the function of BcNS. A total of 34 SWEET genes were identified and they are distributed among ten chromosomes and one scaffold. The Ka/Ks ratio implies that the duplication genes suffered strong purifying selection for retention. These genes were differentially expressed in different floral organs. The phenotypes of the transgenic plants indicated that BcNs participates in the development of the floral nectary. This study provides a basis for further functional analysis of the MtN3/saliva/SWEETs gene family.
MtN3/saliva/SWEET 基因家族成员存在于各种生物体中，并且高度保守。它们的确切生化功能仍不清楚，特别是在白菜中。基于全基因组序列，本研究旨在鉴定白菜中的 MtN3/saliva/SWEETs 家族成员，并分析它们的分类、基因结构、染色体分布、系统发育关系、表达模式和生物学功能。
我们在白菜中鉴定了 34 个 SWEET 基因，并分析了它们在染色体上的定位和相应蛋白质的跨膜区域。系统发育树分析表明，在 Brassica rapa 和 Arabidopsis 分离之前，至少有 17 个假定的祖先基因。这些基因在白菜不同组织和花发育阶段的表达模式表明，它们主要参与生殖发育。B. rapa 中旁系同源 SWEET 基因对的 Ka/Ks 比值远小于 1。在我们之前的研究中，At2g39060 同源基因 Bra000116（BraSWEET9，也称为 BcNS，白菜蜜腺和雄蕊）在白菜花发育过程中发挥了重要作用。洋葱表皮细胞瞬时表达实验表明，该蛋白编码基因定位于质膜。反义表达载体转化的转基因植物表现出基础蜜腺分裂的表型。
本研究首次对白菜 MtN3/saliva/SWEETs 基因进行了序列分析、结构分析、生理生化特性分析，并验证了 BcNS 的功能。共鉴定到 34 个 SWEET 基因，它们分布在 10 条染色体和 1 个支架上。Ka/Ks 比值表明，复制基因受到强烈的纯化选择而得以保留。这些基因在不同的花器官中差异表达。转基因植物的表型表明 BcNs 参与了花蜜腺的发育。本研究为进一步研究 MtN3/saliva/SWEETs 基因家族的功能提供了基础。
