| Fatty acids of plant oils is beneficial for human health and it can be briefly categorized into saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids. According to the position of carbon of the first double bond from the methyl terminus, polyunsaturated fatty acids can be divided into series of n-3, n-6 and so on. a-linolenic acid (ALA), one of the essential fatty acids for human health, plays an important role in regulating blood lipid, lowering blood pressure, blood sugar, preventing cancer, anti-inflammatory, enhancing immunity, protecting vision, and improving memory. Therefore, searching for herbaceous peony (Paeonia lactiflora Pall.) sources rich in ALA, clarifying the related genes and the molecular mechanism in the ALA biosynthesis, can improve the theoretical basis for breeding good varieties and improving ALA content in seed oil. Hence, in this paper, we used GC-MS technology to analyze the fatty acid compositions and the relative content of nine varieties, and the change of the relative content of fatty acids at different developmental periods. Then, two varieties’PL1’and ’PL2’were selected for different content of ALA. We used RACE technology to clone seven related genes in ALA biosynthesis, and analyzed the relationship between the change of fatty acid content and the expression of its related genes in two varieties at different developmental periods. The main results were as follows:(1) The fatty acid compositions of nine varieties at different developmental periods by using GC-MS technology, the results showed that there were fifteen kinds of fatty acids:laurate acid (C12:0), nutmeg acid (C14:0), pentadecane acid (C15:0), palmitic acid (PA, C16:0), palm acid (C16:l),17 alkanes acid (C17:0),17 carbon olefine acid (C17:1), stearic acid (SA, C18:0) and oleic acid (OA, C18:1), linoleic acid (LA, C18:2), ALA (C18:3),10-nonadecyenoic acid (C19:1), arachidic acid (C20:0), peanut acid (C20:1), peanuts diene acid (C20:2). At the seed mature period, total unsaturated fatty acids accounted for more than 90% of the total fatty acids. And there were five main fatty acids which were more than 1%:PA, SA, OA, LA and ALA, the average content of PA, SA, OA, LA and ALA was 5.1%±0.84%,1.44%±0.87%,32.66%±1.78%, 33.44%±3.45% and 26.79%t2.75%, respectively.At the same time, the fatty acids content of nine varieties at different developmental periods was analyzed. In’PL1’, the relative content of PA and SA was always very low and the change tendency was not obvious. The relative content of ALA shew a downward trend, at S1 it was the max (43.76%±6.87%) and the minimum (34.49%±1.53%) at S4. Instead, the relative content of OA was basicly on the rise, it was 20.70%±0.21% at S1 and increased to the max (30.01%±0.48%) at S4. The relative content of LA was also basicly on the rise, increased from 28.35%±8.49% at S1 to 30.13%±1.53% at S4, just decreased slightly at S3. The trend of fatty acids in the other varieties also shew the same.(2) Based on the extraction of RNA in’Hangshao’seeds as a template and the related genes sequence of other plants in Genbank, seven related genes in ALA biosynthesis of P. lactiflora were cloned including PISAD, PIFAD2-1, PIFAD2-2, PIAD3-1, PIFAD3-2, PlFAD6 and PIFAD7. The full-length of cDNAs were 1570bp,1452bp,1466bp,865bp,1685bp,1417bp and 1782bp, encoding 395,383,384,281,435,409 and 448 amino acids, respectively. Homology analysis showed that their amino acids all shared high similarities with those from other plants, and they all had been submitted in GenBank with accession number KJ441080, KJ441081, KM575841, KR605462, KP271029, KP271030 and KP271031, respectively.(3) Through the analysis of fatty acids in nine varieties, two varieties’PL1’and’PL2’were selected for different content of ALA in significance. ALA content in ’PL1’seed oil was the highest (34.49%±1.53%), and in ’PL2’was the lowest (20.08%±1.22%). The expression levels of seven related genes involved in ALA biosynthesis during four seed developmental stages were analyzed by Q-PCR technology. The results suggested that the gene expression in’PL1’with relatively high ALA content is generally higher than that in’PL2’with relatively low ALA content. It also shew that the related genes in ALA biosynthesis were contributed to PISAD, PIFAD2-2 and PIFAD3-1. Compared with’PL2’,’PL1’had higher accumulation of the initial precursor of ALA due to the higher expression level of the three genes. |
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