Guangdong Academy of Forestry, Guangzhou, 510520, China; Guangdong Provincial Key Laboratory of Silviculture, Protection and Utilization, Guangzhou, 510520, China.
Taishan Hongling Seed Orchard, Taishan, Guangdong, 529200, China.
J Plant Physiol. 2024 Dec;303:154359. doi: 10.1016/j.jplph.2024.154359. Epub 2024 Sep 19.
Somatic embryogenesis is a crucial method for achieving clonal forestry in conifers. Understanding the development of zygotic embryos is essential not only for enhancing the efficiency and quality of somatic embryogenesis, but also for advancing forestry breeding programs. This study investigated dynamic changes of element and hormone contents during ZE development of Pinus elliottii and its hybrid P. elliottii × P. caribaea. Significant differences in embryo development speed among different clones were observed. Elemental analysis was conducted using inductively coupled plasma mass spectrometry (ICP-MS) and identified 68 elements, including major, minor, and beneficial elements. In both species, the contents of potassium (K), calcium (Ca), iron (Fe), boron (B) and five beneficial elements decreased during early ZE development, while phosphorus (P) and copper (Cu) increased. Significantly higher levels of K, Ca and Fe at the initial stage, and sulfur (S) and nickel (Ni) decreased at later stages were detected in P. elliottii than in the hybrid. For the other elements, except for very few significant differences at certain stages, most differences between the two species did not reach a significant level. The contents of endogenous hormones were determined and different accumulation patterns were detected in most hormones between the two species, except abscisic acid (ABA) which simultaneously decreased with developments by stage 8. Significant differences were found in indole-3-acetic acid (IAA) contents at most stages between species, while higher levels of total cytokinin (CK) at each stage were detected in the hybrid in comparison with those in P. elliottii. As a result, lower IAA to CK ratios in the hybrid than in P. elliottii. Methyl jasmonate (JA-me) and gibberellin A3 (GA3) contents showed a similar pattern and exhibited an M-shaped fluctuation in the hybrid. Furthermore, JA-me, GA3, gibberellin A4 (GA4) and brassinolide (BR) showed significantly higher levels in the hybrid than in P. elliottii. K-means clustering and correlation analyses were used to explore relationships between elements and hormones during embryo development, revealing complex interplay in both species. These data indicate different requirement in element and hormone contents for embryogenesis and suggest species-specific media composition for each step in somatic embryogenesis. The findings provide insights into their developmental processes and informing future research and applications in somatic embryogenesis and forestry breeding.
体胚发生是实现针叶树克隆林业的关键方法。了解合子胚的发育不仅对于提高体细胞胚胎发生的效率和质量至关重要，而且对于推进林业育种计划也具有重要意义。本研究调查了湿地松及其杂种湿地松×加勒比松胚胎发育过程中元素和激素含量的动态变化。不同无性系胚胎发育速度存在显著差异。采用电感耦合等离子体质谱法（ICP-MS）进行元素分析，共鉴定出 68 种元素，包括大量元素、微量元素和有益元素。在这两个种中，钾（K）、钙（Ca）、铁（Fe）、硼（B）和 5 种有益元素的含量在早期胚胎发育过程中降低，而磷（P）和铜（Cu）的含量增加。在初始阶段，湿地松的 K、Ca 和 Fe 含量显著高于杂种，而 S 和 Ni 的含量在后期阶段降低。除了某些阶段的极少数显著差异外，两个种之间的大多数元素含量差异没有达到显著水平。测定了内源激素的含量，在两个种之间，除了 ABA 外，大多数激素的积累模式不同，ABA 随着发育阶段的进展到第 8 阶段而同时降低。在大多数阶段，种间 IAA 含量存在显著差异，而杂种中各阶段总细胞分裂素（CK）的含量均高于湿地松。因此，杂种中 IAA 与 CK 的比值低于湿地松。茉莉酸甲酯（JA-me）和赤霉素 A3（GA3）的含量呈相似模式，杂种中呈 M 形波动。此外，杂种中 JA-me、GA3、赤霉素 A4（GA4）和油菜素内酯（BR）的含量显著高于湿地松。采用 K-均值聚类和相关性分析探讨了胚胎发育过程中元素和激素之间的关系，揭示了两个种中复杂的相互作用。这些数据表明，胚胎发生对元素和激素含量有不同的要求，并建议为体细胞胚胎发生的每个步骤制定特定于种的培养基组成。研究结果为其发育过程提供了深入了解，并为体细胞胚胎发生和林业育种的未来研究和应用提供了信息。
