The influence of zinc and sulphur deficiency on oil-filling in peanut (Arachis hypogaea L.) kernels

In the developing peanut (Arachis hypogaea L.) kernels, the period between 15 and 35 days after podding (DAP) was identified as the active period of oil-filling. The period of active oil-filling was associated with a decrease in the starch, soluble sugars and proteins so as to make available the energy and carbon skeleton for the synthesis of oil. The oil content in the mature kernels decreased by 11, 12 and 25 per cent with Zn, S and Zn+S deficiency, respectively. In addition, proteins and starch content decreased significantly while that of soluble sugars increased slightly. The activity of malate dehydrogenase and glucose-6-phosphate dehydrogenase also decreased due to Zn as well as S deficiency. The deficiency treatments resulted in a decrease in phospholipids, free fatty acids and triacylglycerols in mature kernels. Further the proportion of 16∶0 and 18∶2 decreased while that of 18∶1 increased in developing kernels.     

Some Morphological and Chemical Characteristics of Developing Fruits of Raphia hookeri

Ndon, B. A. 1985. Some morphological and chemical characteristicsof developing fruits of Raphia hookeri.—J. exp. Bot. 36:1817–1830. Fruits which were at different stages of development were randomlysampled from different inflorescences of Raphia hookeri palms.The morphological characteristics and chemical (the dry matter,lipid and carbohydrate) contents of the exocarp and seeds weredetermined. The results showed that the seed length, circumferenceand volume were optimal at 24 months after pollination whichindicates that Raphia seeds attained maximum size at that period.The seed endosperm was liquid or semi-liquid between 6–18months after pollination but became solid with a prominent embryoat 24 months. The seed dry matter was low at the early stagesof development but there was a rapid increase in seed dry weightat 18–33 months after pollination. The seeds were physiologicallymatured at 30–33 months after pollination, while the exocarpmatured at 24–30 months after pollination. The Raphia seeds were low in lipid (about 2%) compared to theexocarp which had 30–40% lipid at full maturity. Maximumamount of lipid was accumulated within the exocarp at 36–42months after pollination and this period indicates the timefor harvesting Raphia fruits for maximum oil which is probablythe most economic part of the fruit. The total sugar concentration increased in the exocarp withincrease in maturity. Conversely the concentration of sugarsdecreased within the seeds as the fruit matured. Maximum totalsugar concentration (about 309 mg g^–1 dry fat free sample)was found in the exocarp at 36–42 months after pollination.Mature seeds at 48 months after pollination had about 50 mgof total sugars per g of fat free sample. There was insignificantaccumulation of starch in the exocarp. The mature seeds werelow in starch (5–10% of the dry weight). Key words: Raphia hookeri, development, fruit     

Dispersal mode constrains allocation of carbon and mineral nutrients in seeds of forest and savanna trees

• Species vary in seed size and content of stored reserves, which can be related to dispersal strategies and type of habitat in which they are found. We compare seed carbon and nutrient reserves of anemochorous and zoochorous trees from the Cerrado of central Brazil.
• We measured seed dry mass, lipids, non‐structural carbohydrates (starch and total soluble sugars), carbon and mineral nutrients in ten forest and 13 savanna species, each classified as having wind‐ or animal‐dispersed seeds. We used phylogenetically independent contrasts to test for correlations among these traits.
• Seeds of anemochorous species were lighter, with higher concentrations of C, N, P, Ca and Mg. Lipids were the dominant carbon reserve for most anemochorous species, underpinning the importance of allocation to compact carbon reserves. Starch, lipids or soluble sugars were the major carbon reserve in zoochorous seeds. Savanna and forest species did not differ in seed mass or in total carbon reserves. However, seeds of forest species had higher concentrations of starch than seeds of savanna species. Lipid and starch negatively correlated across species, suggesting a trade‐off between starch and lipids as major seed carbon reserves. Calcium was positively correlated with Mn and B, while Mg was positively correlated with C, N, P, K, S, Zn and B. Potassium, S and Cl were positively correlated, while P was positively correlated with Mg and Zn.
• Dispersal mode rather than vegetation type constrained seed mass and seed storage allocation patterns in forest and savanna trees. We provide evidence that similar mechanisms are involved in seed storage of carbon and mineral nutrients across species.

     

Changes in protein and carbohydrate content during development of seeds and siliquas of rapeseed (Brassica napus L.)

Abstract

A study was made on the changes observed in the protein, starch and soluble sugar content during development of siliquas and seeds of rapeseed grown in central Italy.

Concentration of starch and soluble sugars in the seed increases to 75 per cent dry matter during the first few weeks of pod development and then drops to minimum values. The protein increases steadily until maturity, when a level of 0.85 mg per seed is reached, equivalent to 18 per cent dry matter. The protein and starch in the hull? decrease continuously during development, while in the initial stages the soluble sugars are accumulated until they account for 33 per cent dry matter, after which they decline towards maturity.     

Acyl-acyl carrier protein thioesterase activity from sunflower (Helianthus annuus L.) seeds

During sunflower (Helianthus annuus L.) seed formation there was an active period of lipid biosynthesis between 12 and 28 days after flowering (DAF). The maximum in-vitro acyl-acyl carrier protein (ACP) thioesterase activities (EC 3.1.2.14) were found at 15 DAF, preceding the largest accumulation of lipid in the seed. Data from the apparent kinetic parameters, V _max and K _m, from seeds of 15 and 30 DAF, showed that changes in acyl-ACP thioesterase activity are not only quantitative, but also qualitative, since, although the preferred substrate was always oleoyl-ACP, the affinity for palmitoyl-ACP decreased, whereas that for stearoyl-ACP increased with seed maturation. Bisubstrate assays carried out at 30 DAF seemed to indicate that the total activity found in mature seeds is due to a single enzyme with 100/75/15 affinity for oleoyl-ACP/stearoyl-ACP/palmitoyl-ACP. In contrast, at 15 DAF, enzymatic data together with partial sequences from cDNAs indicated the presence of at least two enzymes with different properties, a FatA-like thioesterase, with a high affinity for oleoyl-ACP, plus a FatB-like enzyme, with preference for long-chain saturated fatty acids, both being expressed during the active lipid biosynthesis period. Competition assays carried out with CAS-5, a mutant with a higher content of palmitic acid in the seed oil, indicated that a modified FatA-type thioesterase is involved in the mutant phenotype. Received: 17 December 1999 / Accepted: 25 February 2000     

Changes in carbohydrates,amino acids and proteins in developing seed of chickpea

Developing seeds of chickpea cultivars G-130, L-550 and 850-3/27 grown under field conditions were sampled at different stages of maturity and analysed for soluble sugars, starch, soluble nitrogen, protein nitrogen and amino acids. Fr. wt of seeds of all three cultivars decreased after 28 days of flowering while the dry wt continued to increase. Rapid starch accumulation was observed between 14 and 28 days after flowering. Starch as per cent of seed dry wt started to decrease after 28 days, while starch per seed increased till maturity. The percentage of salt-soluble proteins decreased with maturation of seed. The electrophoretic pattern revealed that deposition of seed storage protein in cotyledons occurred 14 days after flowering. Most of the biochemical activity apparently occurred between 14 and 28 days after flowering.     

Bottlenecks in erucic acid accumulation in genetically engineered ultrahigh erucic acid Crambe abyssinica

Erucic acid is a valuable industrial fatty acid with many applications. The main producers of this acid are today high erucic rapeseed (Brassica napus) and mustard (Brassica juncea), which have 45%–50% of erucic acid in their seed oils. Crambe abyssinica is an alternative promising producer of this acid as it has 55%–60% of erucic acid in its oil. Through genetic modification (GM) of three genes, we have previously increased the level of erucic acid to 71% (68 mol%) in Crambe seed oil. In this study, we further investigated different aspects of oil biosynthesis in the developing GM Crambe seeds in comparison with wild‐type (Wt) Crambe, rapeseed and safflower (Carthamus tinctorius). We show that Crambe seeds have very low phosphatidylcholine‐diacylglycerol interconversion, suggesting it to be the main reason why erucic acid is limited in the membrane lipids during oil biosynthesis. We further show that GM Crambe seeds have slower seed development than Wt, accompanied by slower oil accumulation during the first 20 days after flowering (DAF). Despite low accumulation of erucic acid during early stages of GM seed development, nearly 86 mol% of all fatty acids accumulated between 27 and 50 DAF was erucic acid, when 40% of the total oil is laid down. Likely bottlenecks in the accumulation of erucic acid during early stages of GM Crambe seed development are discussed.     

Characterization of glycolytic initial metabolites and enzyme activities in developing sunflower (Helianthus annuus L.) seeds

Unlike other oilseeds (e.g. Arabidopsis), developing sunflower seeds do not accumulate a lot of starch and they rely on the sucrose that comes from the mother plant to synthesise lipid precursors. Between 10 and 25 days after flowering (DAF), when sunflower seeds form and complete the main period of storage lipid synthesis, the sucrose content of seeds is relatively constant. By contrast, the glucose and fructose content falls from day 20 after flowering and it is always lower than that of sucrose, with glucose being the minor sugar at the end of the seed formation. By studying the apparent kinetic parameters and the activity of glycolytic enzymes in vitro, it is evident that all the components of the glycolytic pathway are present in the crude seed extract. However, in isolated plastids important enzymatic activities are missing, such as the glyceraldehyde-3-phosphate dehydrogenase, involved in the conversion of glyceraldehyde 3-phosphate into 1,3-biphospho-glycerate, or the enolase that converts 2-phosphoglycerate into phosphoenolpyruvate. Hence, phosphoenolpyruvate or one of its derivatives, like pyruvate and malate from the cytosol, may be the primary carbon sources for lipid biosynthesis. Accordingly, the glucose-6-P imported into the plastid is likely to be used in the pentose phosphate pathway to produce the reducing power for lipid biosynthesis in the form of NADPH. Data from crude seed extracts indicate that enolase activity increased during seed formation, from 16 days after flowering, and that this activity was well correlated with the period of storage lipid synthesis. In addition, while the presence of some glycolytic enzymes increased during lipid synthesis, others decreased, remained constant, or displayed irregular temporal behaviour.     

Arabidopsis sucrose synthase 2 and 3 modulate metabolic homeostasis and direct carbon towards starch synthesis in developing seeds

Two genes encoding sucrose synthase (SUS), namely SUS2 (At5g49190) and SUS3 (At4g02280), are strongly and differentially expressed in Arabidopsis seed. Detailed biochemical analysis was carried out in developing seeds 9–21 days after flowering (DAF) of wild type and two knockouts. SUS2 and SUS3 are not redundant genes since single knockouts show a phenotype in developing seeds. The mutants had 30–50% less SUS activity and therefore accumulated 40% more sucrose and 50% less fructose at 15 DAF. This did not affect the hexose-P pool, but led to 30–70% less starch in embryo and seed coat. Lipids were 55% higher in both mutants at 9–15 DAF. It seems that sucrolysis via SUS is not required for oil or protein synthesis but rather for channeling carbon toward ADP-glucose and starch in seeds. Metabolite profiling with GC–TOF revealed specific downstream changes in primary metabolism as a consequence of signaling or regulatory fine-tuning. While sucrose increased, hexoses and specific amino acids decreased reciprocally. There was a developmental shift regarding an earlier timing of dry weight accumulation, germinative maturity, oil deposition, sugar levels, transient starch buildup, and protein storage. Nevertheless, final seed size and composition were unaltered due to an earlier cessation of growth, thus giving rise to an apparent silent phenotype of mature mutant seeds. We conclude that SUS is important for metabolite homeostasis and timing of seed development, and propose that an altered sucrose/hexose ratio can modify carbon partitioning and the pattern of storage compounds in Arabidopsis.     

Lipids in developing and mature rice grain

The neutral fraction of nonstarch lipids in developing brown rice (Oryza sativa L., cv IR42) was accumulated up to 16 days after flowering (DAF), but phospholipids and glycolipids increased only up to 8 DAF. Fatty acids accumulated in nonstarch lipids until 12 DAF. However, the proportion of linolenic acid in the lipid fraction decreased and that of oleic acid increased during this period. Accumulation of fat-by-hydrolysis in the brown rice occurred until 20 DAF and followed closely that of starch. The proportion of linolenic acid decreased and that of linoleic acid increased until 16 DAF. The fatty acid composition of fat-by-hydrolysis and starch lipids were identical and fat-by-hydrolysis accounted for 48% by weight of starch lipids. Nonstarch lipids were mainly composed of triglycerides and were located in the bran and embryo of mature brown rice. Starch lipids were mainly composed of lysophosphatidyl choline, free fatty acids and lysophosphatidyl ethanolamine, and were located in the endosperm.     

14C Photoassimilate Partitioning in Developing Sunflower Seeds

Changes with age of protein and oil content in field-grown Helianthusannuus seeds were followed during the grain filling period.Seeds were sampled from different zones on the flower head:peripheral, intermediate, and central. Regardless of seed position,at maturity protein and oil content accounted for approximately18% and 50% of the dry weight respectively. In an attempt todetermine the importance of the role of photosynthesis in grain-filling,¹⁴CO₂ was incorporated into sunflower leaves and translocatedradioactive photoassimilates in the seed were studied. ¹⁴C-labelledproducts including carbohydrates, nitrogenous compounds andlipids were determined as a function of seed position, lengthof chase period, and seed age. Within 8 h, ¹⁴C-labelled photosynthateis detected in the seed, up to 80% of seed-incorporated radioactivitybeing in the form of free sugars and organic acids. The conversionrate from free sugars to storage compounds (lipids, proteinsand starch) varies according to seed position and age. Lipidsconstitute the major photosynthetic sink, reaching levels ofgreater than 80% of the total seed-incorporated radioactivity.The effects of abscisic acid on uptake and partitioning of ¹⁴Csucrose into immature excised cotyledons were also studied. Key words: Sunflower, photosynthate, abscisic acid     

Increased levels of glycerol-3-phosphate lead to a stimulation of flux into triacylglycerol synthesis after supplying glycerol to developing seeds of<Emphasis Type="Italic"> Brassica napus</Emphasis> L.<Emphasis Type="Italic"> in planta</Emphasis>

Glycerol-3-phosphate (glycerol-3P) is a primary substrate for triacylglycerol synthesis. In the present study, changes in the levels of glycerol-3P during rape (Brassica napus L.) seed development and the influence of manipulating glycerol-3P levels on triacylglycerol synthesis were investigated. (i) Glycerol-3P levels were high in young seeds and decreased during seed development at 30 and 40 days after flowering (DAF), when lipid accumulation was maximal. (ii) To manipulate glycerol-3P levels in planta, various concentrations of glycerol were injected directly into 30-DAF seeds, which remained otherwise intact within their siliques and attached to the plant. Injection of 0–10 nmol glycerol led to a progressive increase in seed glycerol-3P levels within 28 h. (iii). Increased levels of glycerol-3P were accompanied by an increase in the flux of injected [¹⁴C]sucrose into total lipids and triacylglycerol, whereas fluxes to organic acids, amino acids, starch, protein and cell walls were not affected. (iv) When [¹⁴C]acetate was injected into seeds, label incorporation into total lipids and triacylglycerol increased progressively with increasing glycerol-3P levels. (v) There was a strong correlation between the level of glycerol-3P and the incorporation of injected [¹⁴C]acetate and [¹⁴C]sucrose into triacylglycerol. (v) The results provide evidence that the prevailing levels of glycerol-3P co-limit triacylglycerol synthesis in developing rape seeds.Abbreviations DAF Days after flowering - DAG Diacylglycerol - G3PAT Glycerol-3-phosphate acyltransferase - Glycerol-3P Glycerol-3-phosphate - PA Phosphatidic acid - PC Phosphatidylcholine - TAG Triacylglycerol,     

Expression of a modified ADP-glucose pyrophosphorylase large subunit in wheat seeds stimulates photosynthesis and carbon metabolism

ADP-glucose pyrophosphorylase (AGP) is the rate-limiting step in seed starch biosynthesis. Expression of an altered maize AGP large subunit (Sh2r6hs) in wheat (Triticum aestivum L.) results in increased AGP activity in developing seed endosperm and seed yield. The yield phenotype involves increases in both seed number and total plant biomass. Here we describe stimulation of photosynthesis by the seed-specific Sh2r6hs transgene. Photosynthetic rates were increased in Sh2r6hs-expressing plants under high light but not low light growth conditions, peaking at roughly 7 days after flowering (DAF). In addition, there were significant increases in levels of fructose, glucose, and sucrose in flag leaves at both 7 and 14 DAF. In seeds, levels of carbon metabolites at 7 and 14 DAF were relatively unchanged but increases in glucose, ADP-glucose, and UDP-glucose were observed in seeds from Sh2r6hs positive plants at maturity. Increased photosynthetic rates relatively early in seed development appear to be key to the Sh2r6hs enhanced yield phenotype as no yield increase or photosynthetic rate changes were found when plants were grown in a suboptimal light environment. These findings demonstrate that stimulation of biochemical events in both source and sink tissues is associated with Sh2r6hs expression.     

Lipid profiling of developing Jatropha curcas L. seeds using (1)H NMR spectroscopy

Seed development in Jatropha curcas L. was studied with respect to phenology, oil content, lipid profile and concentration of sterols. Seeds were collected at various stages of development starting from one week after fertilization and in an interval of five days thereafter till maturity. These were classified as stage I to stage VII. Moisture content of the seeds ranged from 8.8 to 90.3%; the lowest in mature seeds in stage VII and highest in stage I. The seed area increased as the seed grew from stage I to stage VI (0.2-10.2mm(2) per seed), however, the seed area shrunk at stage VII. Increase in seed area corresponded to increase in fresh weight of the seeds. (1)H NMR spectroscopy of hexane extracts made at different stages of seed development revealed the presence of free fatty acids (FFA), methyl esters of fatty acids (FAME) and triglycerol esters (TAG), along with small quantity of sterols. The young seeds synthesized predominantly polar lipids. Lipid synthesis was noticed nearly three weeks after fertilization. From the fourth week the seeds actively synthesized TAG. Stage III is a turning point in seed development since at this stage, the concentration of sterols decreased to negligible, there was very little FAME formation, accumulation of TAG increased substantially, and there was a sudden decrease in FFA concentration. The findings can be helpful in understanding the biosynthesis and in efforts to improve biosynthesis of TAG and reduce FFA content in the mature seeds.     

Accumulation of Storage Materials,Precocious Germination and Development of Desiccation Tolerance During Seed Maturation in Mustard (Sinapis alba L.)

Under defined environmental conditions (20°C, continuous light of 15 klx) development of mustard seeds from artificial pollination to maturity takes about 60 d. After surpassing the period of embryo cell division and histodifferentiation (12–14d after pollination = dap), the seed enters into a maturation period. The time courses of various physiological, biochemical, and structural changes of embryo and testa during seed maturation were analyzed in detail (dry and fresh mass changes, osmotic and water potential changes, respiration, DNA amplification by endomitosis, total ribosome and polysome formation, storage protein synthesis and accumulation, storage lipid accumulation). In addition to the final storage products protein and lipid, embryo and testa accumulate transiently large amounts of starch within the chloroplasts during early maturation. Concomitantly with the subsequent total breakdown of the starch, the plastids lose most of their internal structure and chlorophyll and shrink into proplastids, typical for the mature seed. At about 30 dap the seeds shift from a desiccation-sensitive to a desiccation-tolerant state and are able then to germinate rapidly upon drying and reimbibition. If isolated from the immature fruit and sown directly on water, the seeds demonstrate precocious germination from about 13 dap onwards. Young seeds (isolated ≦ 38 dap) germinate only after surpassing a lag-phase of several days (after-ripening) during which the embryo continues to accumulate storage protein and lipid at the expense of the surrounding seed tissues. We conclude from these results that the maturing seed represents a rather closed developmental system which is able to continue its development up to successful germination without any specific regulatory influence from the mother plant. Immature seeds are able to germinate without a preceding dehydration treatment, which means that partial or full desiccation does not serve as an environmental signal for reprogramming seed development from maturation to germination. Instead, it is argued that the water relations of the seed are a critical element in the control of maturation and germination: during maturation on the mother plant the embryo is subject to a considerable turgor pressure (of the order of 12 bar) accompanied by a low water potential (of the order of ?12 bar). This turgor permits maturation growth but is subcritical for germination growth. However, upon imbibition in water, the low water potential provides a driving force for a burst of water uptake overcoming the critical turgor threshold and thereby inducing germination.     

Compositional changes in developing rape seed (Brassica napus L.)

Summary The growth and composition of siliquas and seeds of oilseed rape was followed over 12 weeks from shortly after anthesis to maturity. Each plant produced 220 siliquas, this number being constant throughout development. Seed numbers per siliqua fell from 19 to 9 by week 5 and declined to 7 at maturity. Hull¹ and seed growth followed a sigmoid pattern, but were not in phase. Seed development could be divided into 3 phases: In Phase 1, seed weight was low and starch and ethanol soluble compounds accounted for 80% DM. Phase 2, seed growth increased and storage oil and proteins were deposited accounting for 40% and 20% DM respectively at the end of this stage. Starch, glucose and fructose were utilized in this process. Phase 3 was largely concerned with the deposition of oil and protein in fixed proportions. Seed weight more than doubled while DM composition remained constant. Sugars were transferred from the hull to the seed to support this growth.The proportion of hull lipids remained constant throughout development until shortly before maturity when MGDG and DGDG fell due to chloroplast breakdown as indicated by chlorophyll disappearance. The FA composition of the hull lipids resembled that of photosynthetic tissue. In the seeds, the neutral lipids increased from 20% of the total lipids in Phase 1 to 93% at maturity. The proportion of structural lipids declined as the storage lipids increased. In Phase 1 the FA composition of the lipid resembled that of photosynthetic tissue (high in C_16:0; C_18:2; C_18:3). In Phase 2, FA typical of storage triglycerides (C_20:1; C_22:1, appeared, C_18:1 transitorily increased, but C_18:2 and C_18:3 fell dramatically. In Phase 3, the content of C_22:1 continued to rise, but the proportions of the other FA remained constant.Abbreviations DM Dry matter - MGDG Monogalactosyldiglyceride - DGDG Digalactosyldiglyceride - NL Neutral lipid - PC Phosphatidyl choline - PE Phosphatidyl ethanolamine - C_16:0 Palmitic acid - C_18:1 Oleic acid - C_18:2 Linoleic acid - C_18:3 Linolenic acid - C_20:1 Eicosenoic acid - C_22:1 Erucic acid - FA Fatty acid     

Developmental Changes in Relation to Desiccation Tolerance of Archontophoenix alexandrae (Palmae) Seeds

Germination of Archontophoenix alexandrae seeds and embryos were studied under gradient water content treatments throughout the seed development phases of maturation in 2005 to investigate seed desiccation tolerance and storage characteristics. During the maturation process, seed water content decreased gradually from55 DAF (days after flowering) to 70 DAF, and seeds reached the maximum dry-weight at 90 DAF. Seed germinability appeared after 60 DAF. Seeds germinated with a temperature range from15℃- 40℃ under alternating photoperiod (14 h light, 10 h dark, 12μmol m^{- 2}s ^{- 1} ), while the best germination percentage was obtained between 30℃- 35℃. A maximum germination capacity reached at 70 DAF. However, seed germination was greatly inhibited by light. Desiccation tolerance of seeds and embryos increasedgradually from 55 DAF to 90 DAF and reached the maximum at 90 DAF with a semilethal water content of 0.18 g/g ( seed) and 0.3 g/g ( embryo) respectively. Rapid dehydration maintained higher seed germination percentage than thatof slow dehydration when drying to the same water content. Seeds with without water content treatments failed to germinate after 1 month storage under - 18℃, whereas appropriate desiccation treatment prolonged seed longevity under 4℃, 10℃ and 15℃ storage temperatures. It revealed obviously the recalcitrant characteristics of Archontophoenix alexandrae seeds torage behaviour which are tolerant toward neither deep desiccation nor low temperatures.