State Key Laboratory of Tree Genetics and Breeding, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.
Key Laboratory of Forest Genetics and Biotechnology of Ministry of Education, Nanjing Forestry University, Nanjing 210037, China.
Int J Mol Sci. 2024 Jan 4;25(1):669. doi: 10.3390/ijms25010669.
Larch is widely distributed throughout the world and is an important species for timber supply and the extraction of industrial raw materials. In recent years, the hybrid breeding of and has shown obvious heterosis in quick-growth, stress resistance and wood properties. However, its growth and development cycle is too long to meet general production needs. In order to shorten the breeding cycle, we have for the first time successfully established and optimized a somatic embryogenesis system for × . We found that the highest rate of embryonal-suspensor mass (ESM) induction was observed when late cotyledonary embryos were used as explants. The induced ESMs were subjected to stable proliferation, after which abscisic acid (ABA) and polyethylene glycol (PEG) were added to successfully induce somatic embryos. Treatment with PEG and ABA was of great importance to somatic embryo formation and complemented each other's effect. ABA assisted embryo growth, whereas PEG facilitated the formation of proembryo-like structures. On top of this, we studied in more detail the relationship between redox homeostasis and the efficiency of somatic embryogenesis (frequency of ESM induction). During subculture, we observed the gradual formation of three distinct types of ESM. The Type I ESM is readily able to form somatic embryos. In contrast to type I, the type III ESM suffers from severe browning, contains a higher level of hydrogen peroxide (HO) and demonstrates a decreased ability to form somatic embryos. External treatment with HO decreased the somatic embryogenesis efficiency of Type I and type III ESMs, or the higher the exogenous HO content, the lower the resulting somatic embryogenesis efficiency. We found that treatment with the HO scavenger DMTU (dimethylthiourea) could significantly increase the somatic embryogenesis efficiency of the type III ESM, as a result of a decline in endogenous HO content. Overall, these findings have contributed to setting up a successful somatic embryogenesis system for larch production.
落叶松广泛分布于世界各地，是提供木材和工业原料的重要物种。近年来，与 的杂种杂交在快速生长、抗逆性和木材特性方面表现出明显的杂种优势。然而，其生长发育周期过长，无法满足一般生产需求。为了缩短育种周期，我们首次成功建立并优化了落叶松 × 杂种的体细胞胚胎发生系统。我们发现，以晚期子叶期胚胎作为外植体时，胚性-悬浮胚体（ESM）诱导率最高。诱导的 ESM 进行稳定增殖后，添加脱落酸（ABA）和聚乙二醇（PEG）成功诱导体细胞胚。PEG 和 ABA 的处理对体细胞胚的形成非常重要，它们相互补充。ABA 有助于胚胎生长，而 PEG 则有利于原胚样结构的形成。此外，我们更详细地研究了氧化还原稳态与体细胞胚胎发生效率（ESM 诱导频率）之间的关系。在继代培养过程中，我们观察到三种不同类型的 ESM 逐渐形成。I 型 ESM 很容易形成体细胞胚。与 I 型相比，III 型 ESM 褐变严重，过氧化氢（HO）含量较高，形成体细胞胚的能力降低。外源性 HO 处理降低了 I 型和 III 型 ESM 的体细胞胚胎发生效率，或者外源 HO 含量越高，体细胞胚胎发生效率越低。我们发现，HO 清除剂 DMTU（二甲基硫脲）处理可以显著提高 III 型 ESM 的体细胞胚胎发生效率，因为内源 HO 含量下降。总之，这些发现为落叶松生产成功建立了体细胞胚胎发生系统。
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