Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos, 29071 Málaga, Spain.
Institut Technologique FCBA, Pôle Biotechnologies et Sylviculture Avancée (BSA), 71 Route d'Arcachon, Pierroton, 33610 Cestas, France.
Tree Physiol. 2018 Mar 1;38(3):471-484. doi: 10.1093/treephys/tpx133.
Vegetative propagation through somatic embryogenesis is critical in conifer biotechnology towards multivarietal forestry that uses elite varieties to cope with environmental and socio-economic issues. An important and still sub-optimal process during in vitro maturation of somatic embryos (SE) is the biosynthesis and deposition of storage proteins, which are rich in amino acids with high nitrogen (N) content, such as arginine. Mobilization of these N-rich proteins is essential for the germination and production of vigorous somatic seedlings. Somatic embryos accumulate lower levels of N reserves than zygotic embryos (ZE) at a similar stage of development. To understand the molecular basis for this difference, the arginine metabolic pathway has been characterized in maritime pine (Pinus pinaster Ait.). The genes involved in arginine metabolism have been identified and GFP-fusion constructs were used to locate the enzymes in different cellular compartments and clarify their metabolic roles during embryogenesis and germination. Analysis of gene expression during somatic embryo maturation revealed high levels of transcripts for genes involved in the biosynthesis and metabolic utilization of arginine. By contrast, enhanced expression levels were only observed during the last stages of maturation and germination of ZE, consistent with the adequate accumulation and mobilization of protein reserves. These results suggest that arginine metabolism is unbalanced in SE (simultaneous biosynthesis and degradation of arginine) and could explain the lower accumulation of storage proteins observed during the late stages of somatic embryogenesis.
通过体细胞胚胎发生进行营养繁殖对于利用优良品种应对环境和社会经济问题的多品种林业的针叶树生物技术至关重要。在体细胞胚胎（SE）体外成熟过程中，一个重要但仍不理想的过程是储存蛋白的生物合成和沉积，这些蛋白富含具有高氮（N）含量的氨基酸，如精氨酸。这些富含 N 的蛋白质的动员对于种子的萌发和活力体细胞苗的产生是必不可少的。在相似的发育阶段，体细胞胚胎积累的 N 储备水平低于合子胚（ZE）。为了了解这种差异的分子基础，已经对欧洲赤松（Pinus pinaster Ait.）中的精氨酸代谢途径进行了表征。已经鉴定了参与精氨酸代谢的基因，并使用 GFP 融合构建体来定位不同细胞区室中的酶，并阐明它们在胚胎发生和萌发过程中的代谢作用。对体细胞胚胎成熟过程中的基因表达分析表明，参与精氨酸生物合成和代谢利用的基因的转录本水平较高。相比之下，仅在 ZE 的成熟和萌发的最后阶段观察到增强的表达水平，这与蛋白质储备的充足积累和动员一致。这些结果表明，在 SE 中（精氨酸的同时生物合成和降解）精氨酸代谢不平衡，这可以解释在体细胞胚胎发生的后期观察到的储存蛋白积累较少的现象。
