Table_1_Temperature and Water Availability During Maturation Affect the Cytokinins and Auxins Profile of Radiata Pine Somatic Embryos.docx

Somatic embryogenesis (SE) provides us a potent biotechnological tool to manipulate the physical and chemical conditions (water availability) along the process and to study their effect in the final success in terms of quantity of somatic embryos produced. In the last years, our research team has been focused on the study of different aspects of the SE in Pinus spp. One of the main aspects affecting SE is the composition of culture media; in this sense, phytohormones play one of the most crucial roles in this propagation system. Many studies in conifers have shown that different stages of SE and somatic embryo development are correlated with distinct endogenous phytohormone profiles under the stress conditions needed for the process (i.e., cytokinins play a regulatory role in stress signaling, which it is essential for radiata pine SE). Based on this knowledge, the aim of this study was to test the effect of different temperatures (18, 23, and 28°C) and gelling agent concentrations (8, 9, and 10 gL-1) during the maturation stage of Pinus radiata SE in maturation and germination rates. Parallel, phytohormone profile of somatic embryos developed was evaluated. In this sense, the highest gellan gum concentration led to significantly lower water availability. At this gellan gum concentration and 23°C a significantly higher number of somatic embryos was obtained and the overall success of the process increased with respect to other treatments assayed. The somatic embryos produced in these conditions showed the highest concentration of iP-type cytokinins and total ribosides. Although, the different conditions applied during maturation of somatic embryos led to different hormonal profiles, they did not affect the ex vitro survival of the resulting somatic plants, where no significant differences were observed.

体细胞胚胎发生（Somatic embryogenesis，SE）是一种高效的生物技术手段，可用于调控整个过程中的物理与化学参数（如水分可用性），并探究这些参数对体细胞胚胎产出量这一最终成功指标的影响。近年来，本研究团队长期聚焦于松属（Pinus spp.）植物体细胞胚胎发生的多维度研究。培养基组成是影响体细胞胚胎发生的核心因素之一，而植物激素在该繁殖体系中发挥着最为关键的调控作用。诸多针对针叶树的研究表明，体细胞胚胎发生的不同阶段及体细胞胚胎发育进程，与该过程所需胁迫条件下的内源植物激素谱密切相关——例如，细胞分裂素在胁迫信号转导中扮演调控角色，而这对于辐射松（Pinus radiata）的体细胞胚胎发生至关重要。基于上述研究基础，本研究旨在测试不同温度（18、23和28℃）及凝胶剂浓度（8、9和10 g·L⁻¹）对辐射松体细胞胚胎发生成熟阶段的胚胎成熟效果与萌发率的影响；同时，对所获得的体细胞胚胎的植物激素谱进行检测分析。研究发现，较高的结冷胶（gellan gum）浓度会显著降低培养基的水分可用性。在该结冷胶浓度且温度为23℃的处理组中，可获得显著更多的体细胞胚胎，且该流程的整体成功率相较于其他受试组均有所提升。在此条件下生成的体细胞胚胎，其异戊烯腺嘌呤型细胞分裂素（iP-type cytokinins）及总核苷的含量均为最高。尽管成熟阶段施加的不同培养条件会导致体细胞胚胎的激素谱产生差异，但这些条件并未对后续获得的体细胞植株的离体（ex vitro）成活率造成显著影响。