Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Baodao Xincun, Danzhou, Hainan, 571737, China.
State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing, 100871, China.
BMC Plant Biol. 2018 Jan 9;18(1):10. doi: 10.1186/s12870-017-1203-3.
Breeding rubber tree seedling with growth heterosis is vital for natural rubber production. It is the prerequisites for effectively utilizing growth heterosis to elucidate its molecular mechanisms, but the molecular mechanisms remain poorly understood in rubber tree. To elucidate seedling growth heterosis, we conducted comparative transcriptomic analyses between the two hybrids and their parents.
By identifying and comparing differently expressed genes (DEGs), we found that the hybrids (BT 3410 and WC 11) show significantly differential expression profiles from their parents (PR 107 and RRIM 600). In BT 3410-parent triad, 1092 (49.95%) and 1094 (50.05%) DEGs indicated clear underdominance or overdominance, respectively. Whereas in WC 11-parent triad, most DEGs (78.2%, 721) showed low- or high-parent dominance; 160 (17.35%) exhibited expression patterns that are not statistically distinguishable from additivity, and 8 (0.87%) and 33 (3.58%) DEGs exhibited underdominance and overdominance, respectively. Furthermore, some biological processes are differentially regulated between two hybrids. Interestingly, the pathway in response to stimulus is significantly downregulated and metabolic pathways are more highly regulated in BT 3410.
Taken together, the genotypes, transcriptomes and biological pathways (especially, carbohydrate metabolism) are highly divergent between two hybrids, which may be associated with growth heterosis and weakness. Analyzing gene action models in hybrid-parent triads, we propose that overdominance may play important roles on growth heterosis, whereas dominance on hybrid weakness in rubber tree seedlings. These findings bring new insights into our understanding of growth heterosis of rubber tree seedling.
培育具有生长杂种优势的橡胶树幼苗对天然橡胶生产至关重要。这是有效利用生长杂种优势阐明其分子机制的前提条件，但橡胶树的分子机制仍知之甚少。为了阐明幼苗生长杂种优势，我们对两个杂种及其亲本进行了比较转录组分析。
通过鉴定和比较差异表达基因（DEGs），我们发现杂种（BT 3410 和 WC 11）与亲本（PR 107 和 RRIM 600）的表达谱存在显著差异。在 BT 3410-亲本三联体中，分别有 1092 个（49.95%）和 1094 个（50.05%）DEGs 显示明显的下位优势或上位优势。而在 WC 11-亲本三联体中，大多数 DEGs（78.2%，721）表现出低亲或高亲优势；160 个（17.35%）表现出与加性无统计学差异的表达模式，8 个（0.87%）和 33 个（3.58%）DEGs 分别表现出下位优势和上位优势。此外，两个杂种之间有一些生物过程存在差异调控。有趣的是，对刺激的反应途径显著下调，BT 3410 中的代谢途径受到更高的调控。
总之，两个杂种之间的基因型、转录组和生物途径（特别是碳水化合物代谢）高度分化，这可能与生长杂种优势和弱势有关。通过分析杂种-亲本三联体中的基因作用模型，我们提出上位优势可能在橡胶树幼苗的生长杂种优势中起重要作用，而显性优势可能在杂种弱势中起作用。这些发现为我们理解橡胶树幼苗的生长杂种优势提供了新的见解。
