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Transcriptomics of developing wild sunflower seeds from the extreme ends of a latitudinal gradient differing in seed oil composition.

ABSTRACT: Seed oil composition, an important agronomic trait in cultivated sunflower, varies latitudinally across the native range of its wild progenitor. This pattern is thought to be driven by selection for a higher proportion of saturated fatty acids in southern populations compared with northern populations, likely due to the different temperatures experienced during seed germination. To investigate whether these differences in fatty acid composition between northern and southern populations correspond to transcriptional variation in the expression of genes involved in fatty acid metabolism, we sequenced RNA from developing seeds of sunflowers from Texas, USA, and Saskatchewan, Canada (the extreme ends of sunflower's latitudinal range) grown in a common garden. We found 4,741 genes to be differentially expressed between Texas and Canada, including several genes involved in lipid metabolism. Several differentially expressed lipid metabolism genes also colocalized with known oil quantitative trait loci (QTL). The genes producing stearoyl-ACP-desaturases (SAD) were of particular interest because of their known role in the conversion of fully saturated into unsaturated fatty acids. Two SAD genes were more highly expressed in seeds from Canadian populations, consistent with the observation of increased levels of unsaturated fatty acids in seeds from that region. We also constructed a gene co-expression network to investigate regional variation in network modules. The results of this analysis revealed regional differentiation for eight of 12 modules but no clear relationship with oil biosynthesis. Overall, the differential expression of SAD genes offers a partial explanation for the observed differences in seed oil composition between Texas and Canada, while the expression patterns of other metabolic genes suggest complex regulation of fatty acid production and usage across latitudes.

SUBMITTER: Barnhart MH

PROVIDER: S-EPMC9307388 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:: Seed-borne fungi in 69 sunflower cultivars were evaluated which comprised 52 confectionery and 17 oilseed types. Seed coats were placed on both NP-10 (Nonylphenol Ethoxylate based surfacant -10) and potato dextrose agar (PDA) media to culture fungi. The rate of contamination among the different varieties was calculated by counting seed coats with fungal colonies. The rate of contamination in the confectionary group (88%) was significantly (p ≤ 0.05) higher than in the oilseed group (71%). Of the 52 confectionery varieties, the dominant fungi recovered were Verticillium dahliae along with Alternaria spp., Fusarium spp., and Rhizopus spp., whereas the oilseed type varieties were contaminated with only V. dahliae. Molecular identification of fungal species via BLAST (Basic Alignment Search Tool) was performed on fungal sequences obtained from PCR (Polymerase Chain Reaction) analysis. The results included five Alternaria spp. that included Alternaria tenuissima, Alternaria alternata, Alternaria helianthiinficiens, Alternaria longipes, and Alternaria tamaricis, three Fusarium spp. such as Fusarium oxysporum, Fusarium incarnatum, and Fusarium proliferatum, and V. dahliae and Cladosporium cladosporioides. These were identified from pure fungal cultures recovered from seed coats. To efficiently control seed-borne fungi, four broad spectrum fungicides (carbendazim, triadimefon, caprio F-500, and flusilazole) were screened against V. dahliae isolate Gn3, which was isolated from a diseased LD 5009 sunflower plant. Flusilazole was selected based on its low half-maximal effective concentration value (EC50), 78.7 µg/mL. Seeds of diseased LD 5009 plants obtained from two different locations treated with formulated flusilazole fungicide at optimum parameters showed a significant (p ≤ 0.05) increase in seed germination and a decrease in contamination rate from 98% to less than 10%. The results affirmed that confectionery cultivars are much more susceptible to fungal contamination than oilseeds, and also that seed pretreatment is a suitable way to prevent the spread of soil- and seed-borne fungi in sunflower production.

Project description:IntroductionSunflower seeds possess higher oil content than do cereal crop seeds. Storage of sunflower seeds is accompanied by loss of seed vigor and oxidation of storage and membrane lipids.ObjectivesThis study first reported that compound sodium nitrophenolate (CSN), a new plant growth modulator, improved the germination and seedling emergence of aged sunflower seeds. The present study provide a future reference as to the potential applications of CSN and the regulation mechanism of exogenous substances in increasing aged crop seed vigor.MethodsPhenotypic analysis was performed to investigate the effect of CSN on germination and seedling emergence from naturally- and artificially-aged sunflower seeds. The biochemical and enzyme activity analysis were conducted to test the CSN-induced effect on glycometabolism, fatty acid and abscisic acid metabolism. Meanwhile, gene expression analysis was carried out to detect the changes in the transcription level of sunflower seeds during early germination period after CSN treatment.ResultsCSN application significantly increased the germination rate and seedling emergence rate of sunflower seeds under natural and artificial aging. Biochemical analysis indicated that, CSN treatment significantly enhanced the sucrose and fructose contents in aged sunflower seeds during early germination period. Moreover, the contents of several different fatty acids in CSN-treated sunflower seeds also significantly increased. Enzyme activity analysis revealed that CSN treatment remarkably up-regulated the activities of several critical enzymes related to triacylglycerol hydrolysis. Consequently, the transcription levels of the above key enzymes-related synthetic genes were also significantly up-regulated in CSN treatment. Furthermore, CSN treatment significantly decreased abscisic acid (ABA) content through the regulation of the gene expressions and activities of metabolism related-enzymes.ConclusionTaken together, the contribution of CSN to the improvement of aged sunflower seed germination and seedling emergence might be closely related to the fatty acid, glycometabolism, and ABA metabolism.

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Transcriptomics of developing wild sunflower seeds from the extreme ends of a latitudinal gradient differing in seed oil composition.

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