RESUMEN
Sapium sebiferum (L.) Roxb. is an important woody oil tree and traditional herbal medicine in China. Stearoyl-acyl carrier protein desaturase (SAD) is a dehydrogenase enzyme that plays a key role in the transformation of saturated fatty acids into unsaturated fatty acids in oil; these fatty acids greatly influence the freezing tolerance of plants. However, it remains unclear whether freezing tolerance can be regulated by the expression level of SsSAD in S. sebiferum L. Our research indicated that SsSAD expression in S. sebiferum L. increased under freezing stress. To further confirm this result, we constructed a pEGAD-SsSAD vector and transformed it into B. napus L. W10 by Agrobacterium tumefaciens-mediated transformation. Transgenic plants that overexpressed the SsSAD gene exhibited significantly higher linoleic (18:2) and linolenic acid (18:3) content and advanced freezing tolerance. These results suggest that SsSAD overexpression in B. napus L. can increase the content of polyunsaturated fatty acids (PUFAs) such as linoleic (18:2) and linolenic acid (18:3), which are likely pivotal in improving freezing tolerance in B. napus L. plants. Thus, SsSAD overexpression could be useful in the production of freeze-tolerant varieties of B. napus L.
Asunto(s)
Brassica napus/fisiología , Oxigenasas de Función Mixta/metabolismo , Sapium/genética , Secuencia de Aminoácidos , Brassica napus/genética , Congelación , Oxigenasas de Función Mixta/genética , Plantas Modificadas Genéticamente , Sapium/enzimología , Alineación de SecuenciaRESUMEN
Aimed to understand the waterlogging tolerance and adaptation mechanisms of different tree species, a simulated field experiment was conducted to study the growth and energy-metabolic enzyme activities of one-year-old seedlings of Taxodium distichum, Carya illinoensis, and Sapium sebiferum. Three treatments were installed, i. e., CK, waterlogging, and flooding, with the treatment duration being 60 days. Under waterlogging and flooding, the relative growth of test tree species was in the order of T. distichum > C. illinoensis > S. sebiferum, indicating that T. distichum had the strongest tolerance against waterlogging and flooding, while S. sebiferum had the weakest one. Also under waterlogging and flooding, the root/crown ratio of the three tree species increased significantly, suggesting that more photosynthates were allocated in roots, and the lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH) activities of the tree species also had a significant increase. Among the test tree species, T. distichum had the lowest increment of LDH and ADH activities under waterlogging and flooding, but the increment could maintain at a higher level in the treatment duration, while for C. illinoensis and S. sebiferum, the increment was larger during the initial and medium period, but declined rapidly during the later period of treatment. The malate dehydrogenase (MDH), phosphohexose (HPI), and glucose-6-phosphate dehydrogenase (G6PDH) -6-phosphogluconate dehydrogenase (6PGDH) activities of the tree species under waterlogging and flooding had a significant decrease, and the decrement was the largest for T. distichum, being 35.6% for MDH, 21.0% for HPI, and 22.7% for G6PDH - 6PGDH under flooding. It was suggested that under waterlogging and flooding, the tree species with strong waterlogging tolerance had a higher ability to maintain energy-metabolic balance, and thus, its growth could be maintained at a certain level.
Asunto(s)
Metabolismo Energético/fisiología , Suelo/análisis , Árboles/enzimología , Árboles/crecimiento & desarrollo , Agua/análisis , Adaptación Fisiológica , Carya/enzimología , Carya/crecimiento & desarrollo , Inundaciones , Glucosafosfato Deshidrogenasa/metabolismo , Malato Deshidrogenasa/metabolismo , Sapium/enzimología , Sapium/crecimiento & desarrollo , Plantones/enzimología , Plantones/crecimiento & desarrollo , Especificidad de la Especie , Taxodium/enzimología , Taxodium/crecimiento & desarrolloRESUMEN
A full-length cDNA (SsFAD3) for an omega-3 fatty acid desaturase (omega-3 FAD) was cloned from Sapium sebiferum (L.) Roxb. using rapid amplification of cDNA ends and reverse transcription polymerase chain reaction methods. SsFAD3 contained a 1119-bp open reading frame encoding a 372-amino acid polypeptide. The genomic sequence region of the SsFAD3 ORF was composed of 8 exons and 7 introns, similar to other omega-3 FADs found in most plants. The amino acid sequence showed a higher identity with microsomal omega-3 FADs than plastidial omega-3 FADs. Southern blot analysis of SsFAD3 suggested the existence of a small gene family composed of several copies or closely linked genes. SsFAD3 transcripts were detected in shoots, roots, leaves, stems, and seeds, but were most abundant in shoots. The function of SsFAD3 was confirmed by the accumulation of alpha-linolenic acid (alpha-18:3) in Saccharomyces cerevisiae transformants.
Asunto(s)
Biotecnología/métodos , Ácido Graso Desaturasas/química , Regulación Enzimológica de la Expresión Génica , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/genética , Sapium/enzimología , Secuencia de Bases , Southern Blotting , Clonación Molecular , Cartilla de ADN/química , ADN Complementario/química , Exones , Ácido Graso Desaturasas/genética , Intrones , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , ARN Mensajero/metabolismoRESUMEN
A new full-length cDNA (Ssd12) encoding a Delta12-fatty acid desaturase (Delta12-FAD) was cloned from Sapium sebiferum using RT-PCR and RACE methods. Ssd12 contained a 1146 bp open reading frame encoding a protein of 381 amino acids. The amino acid sequence showed a much higher match with microsomal Delta12-FAD amino acid sequences than chloroplast Delta12-FAD amino acid sequences. Genomic Southern blot analysis suggested that Ssd12 had at least two copies. Ssd12 transcripts were detected in roots, leaves, stems, and seeds by real time PCR.