Castander-Olarieta Ander, Pereira Cátia, Montalbán Itziar A, Mendes Vera M, Correia Sandra, Suárez-Álvarez Sonia, Manadas Bruno, Canhoto Jorge, Moncaleán Paloma
Department of Forestry Science, NEIKER, Arkaute, Spain.
Center for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
Front Plant Sci. 2021 Apr 12;12:631239. doi: 10.3389/fpls.2021.631239. eCollection 2021.
Somatic embryogenesis is the process by which bipolar structures with no vascular connection with the surrounding tissue are formed from a single or a group of vegetative cells, and in conifers it can be divided into five different steps: initiation, proliferation, maturation, germination and acclimatization. Somatic embryogenesis has long been used as a model to study the mechanisms regulating stress response in plants, and recent research carried out in our laboratory has demonstrated that high temperatures during initial stages of conifer somatic embryogenesis modify subsequent phases of the process, as well as the behavior of the resulting plants . The development of high-throughput techniques has facilitated the study of the molecular response of plants to numerous stress factors. Proteomics offers a reliable image of the cell status and is known to be extremely susceptible to environmental changes. In this study, the proteome of radiata pine somatic embryos was analyzed by LC-MS after the application of high temperatures during initiation of embryonal masses [(23°C, control; 40°C (4 h); 60°C (5 min)]. At the same time, the content of specific soluble sugars and sugar alcohols was analyzed by HPLC. Results confirmed a significant decrease in the initiation rate of embryonal masses under 40°C treatments (from 44 to 30.5%) and an increasing tendency in the production of somatic embryos (from 121.87 to 170.83 somatic embryos per gram of embryogenic tissue). Besides, heat provoked a long-term readjustment of the protein synthesis machinery: a great number of structural constituents of ribosomes were increased under high temperatures, together with the down-regulation of the enzyme methionine-tRNA ligase. Heat led to higher contents of heat shock proteins and chaperones, transmembrane transport proteins, proteins related with post-transcriptional regulation (ARGONAUTE 1D) and enzymes involved in the synthesis of fatty acids, specific compatible sugars (myo-inositol) and cell-wall carbohydrates. On the other hand, the protein adenosylhomocysteinase and enzymes linked with the glycolytic pathway, nitrogen assimilation and oxidative stress response were found at lower levels.
体细胞胚胎发生是指由单个或一组营养细胞形成与周围组织无维管连接的双极结构的过程，在针叶树中，它可分为五个不同阶段：起始、增殖、成熟、萌发和驯化。长期以来，体细胞胚胎发生一直被用作研究植物应激反应调控机制的模型，我们实验室最近的研究表明，针叶树体细胞胚胎发生初始阶段的高温会改变该过程的后续阶段以及所产生植株的行为。高通量技术发展推动了对植物对多种应激因素分子反应的研究。蛋白质组学提供了细胞状态的可靠图景，并且已知极易受到环境变化的影响。在本研究中，在胚性愈伤组织起始阶段施加高温（23℃，对照；40℃（4小时）；60℃（5分钟））后，通过液相色谱-质谱联用仪分析辐射松体细胞胚的蛋白质组。同时，通过高效液相色谱法分析特定可溶性糖和糖醇的含量。结果证实，40℃处理下胚性愈伤组织的起始率显著降低（从44%降至30.5%），体细胞胚产量呈上升趋势（从每克胚性组织121.87个体细胞胚增至170.83个）。此外，热应激引发了蛋白质合成机制的长期调整：高温下核糖体的大量结构成分增加，同时甲硫氨酸-tRNA连接酶的活性下调。热应激导致热休克蛋白和伴侣蛋白、跨膜转运蛋白、与转录后调控相关的蛋白质（AGO1D）以及参与脂肪酸、特定相容性糖（肌醇）和细胞壁碳水化合物合成的酶含量升高。另一方面，发现腺苷同型半胱氨酸酶以及与糖酵解途径、氮同化和氧化应激反应相关的酶含量较低。
