International College, Huazhong Agricultural University, Lion Mountain, Wuhan, China.
Institute of Tropical Bioscience and Biotechnology, MOA Key Laboratory of Tropical Crops Biology and Genetic Resources, Hainan Bioenergy Center, CATAS, Haikou, Hainan Province, China.
PLoS One. 2019 Apr 1;14(4):e0214335. doi: 10.1371/journal.pone.0214335. eCollection 2019.
The rubber tree (Hevea brasiliensis Muell. Arg.) is a rubber producing crop and contains specialized laticifers. MADS-box genes are a family of transcription factor genes that regulate plant development, especially floral organ and gametophyte development. 97 MADS-box genes were identified in the rubber tree through transcriptomes and genome mining. 93.8% of the genes were mapped onto the genome scaffolds in correspondence to the coverage (93.8%) of current version of sequenced genome. Phylogenetic analysis indicates that type II MADS-box genes have been more actively duplicated than their orthologous genes in Arabidopsis and rice, so that most (70, 72.2%) of the MADS-box genes in the rubber tree belong to type II subfamily. This is a high percentage compared to those in Arabidopsis (43.7%) and rice (56.8%). Moreover, 69 out of 70 type II genes in the rubber tree are transcribed, and they are mostly predominantly expressed in flowers, but some genes are predominantly expressed in laticifers, suggesting their roles in both flower and laticifer development. The number of type I genes in the rubber tree is only 27 (27.8%), a much smaller number compared to their orthologous genes in Arabidopsis (56.3%) and rice (43.2%). At the same time, most of the type I genes (55.6%, 15) in the rubber tree are silent and are probably pseudogenes. The high birth rate and low death rate of type II genes and low birth rate and high death rate of type I genes may corresponds to special developmental requirements in the rubber tree, e.g. the development of laticifer system for biosynthesis of cis-polyisoprene, the rubber. Moreover, atypical MIKC* factors (e.g. HbMADS1 in S-clade, and HbMADS20 in P-clade) are identified. These genes are diverged to typical MIKC* genes in sequences and facilitate functions required in laticifer development and rubber biosynthesis, which is not necessary in Arabidopsis and rice.
橡胶树（Hevea brasiliensis Muell. Arg.）是一种产胶作物，含有专门的乳汁管。MADS 框基因是一类调节植物发育的转录因子基因，特别是花器官和配子体发育。通过转录组和基因组挖掘，在橡胶树中鉴定出 97 个 MADS 框基因。93.8%的基因与当前测序基因组版本的覆盖率（93.8%）相对应，映射到基因组支架上。系统发育分析表明，与拟南芥和水稻的同源基因相比，II 型 MADS 框基因的复制更为活跃，因此橡胶树中的大多数（70，72.2%）MADS 框基因属于 II 型亚家族。与拟南芥（43.7%）和水稻（56.8%）相比，这一比例很高。此外，橡胶树中的 70 个 II 型基因中有 69 个被转录，它们主要在花中表达，但有些基因主要在乳汁管中表达，这表明它们在花和乳汁管发育中都有作用。橡胶树中 I 型基因的数量只有 27 个（27.8%），与拟南芥（56.3%）和水稻（43.2%）的同源基因相比，数量要少得多。同时，橡胶树中的大多数 I 型基因（55.6%，15 个）是沉默的，可能是假基因。II 型基因的高出生率和低死亡率以及 I 型基因的低出生率和高死亡率可能对应于橡胶树特殊的发育需求，例如为合成顺式聚异戊二烯（橡胶）而合成的乳汁管系统的发育。此外，还鉴定出非典型的 MIKC因子（例如 S 族中的 HbMADS1 和 P 族中的 HbMADS20）。这些基因在序列上与典型的 MIKC基因分化，并促进乳汁管发育和橡胶生物合成所需的功能，而这在拟南芥和水稻中是不必要的。
