Sorbitol accumulation during natural and accelerated ageing of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) seeds

The aim of the present study was to determine the effect of accelerated ageing on the composition and content of the soluble carbohydrates in pea seeds of six genotypes differing in the composition of raffinose family oligosaccharides. A gradual decrease in the concentration of higher homologues of raffinose was observed along with seed ageing. At the same time the seeds lost vigor, viability and germination capacity. No increase in the concentration of reducing sugars was recorded, but sorbitol accumulated in pea embryos. Sorbitol accumulation may indicate seed quality deterioration during storage.     

Changes in starch,oligosaccharides and soluble sugars in developing pod wall and seed of chickpea

The accumulation of starch in the seed of chickpea accompanied by a decline in the pod wall during the early stages of development probably indicates that seed and pod wall did not compete with each other for starch accumulation. During the early stages of maturation, the reducing and non-reducing sugars showed a decline in seeds whereas non-reducing sugars decreased in the pod wall. The accumulation of the oligosaccharides raffinose, stachyose, and some other unidentified oligosaccharides was accompanied by a decline in the mono- and disaccharides in the developing seeds.     

Sugar utilization by developing wild type and shrunken-2 maize kernels

To characterize the movement of sugars during kernel development in maize, a newly devised in vitro kernel development scheme was utilized. Viable seeds of wild type maize (Zea mays L.) as well as the mutant shrunken-2 (sh2) were found to mature when grown in culture with reducing sugars or sucrose as the carbon source. However, wild type and sh2 kernels had greater germination, starch content, and seed weight when sucrose, rather than reducing sugars, was the carbon source. By the use of labeled sucrose it was shown that sucrose can move into endosperm tissue without intervening degradation and resynthesis. These results show that when grown in vitro the maize seed can utilize reducing sugars for development, but it prefers sucrose.     

Changes in soluble sugars in relation to desiccation tolerance and effects of dehydration on freezing characteristics of Acer platanoides and Acer pseudoplatanus seeds

The role of soluble sugars in desiccation tolerance was investigated in seeds of two species from the genus Acer: Norway maple (Acer platanoides L.) — tolerant and sycamore (Acer pseudoplatanus L.) — intolerant to dehydration. During two years of observations it was found that seeds of Norway maple acquire desiccation tolerance at the end of August i.e. about 125 days after flowering (DAF). During seed development, the transition from intolerant to tolerant state in Norway maple seeds was accompanied by the accumulation in seed tissues of raffinose, stachyose and sucrose. The sucrose/raffinose ratio in Norway maple seeds was lower than in sycamore. In mature Norway maple seeds sucrose and raffinose contents were higher than in sycamore. It was concluded, that soluble sugars such as sucrose, raffinose and stachyose may play an important role in desiccation tolerance and/or intolerance of Norway maple and sycamore seeds. Differential thermal analysis (DTA) was used to study the relationship between desiccation sensitivity and the state of water in seed tissues. The level of non-freezable water was the same in both analysed seed species, but the temperature of water crystallization during desiccation was lower in sycamore seeds.     

Changes in sugars during rice seed desiccation

The correlation between desiccation tolerance and soluble sugars was investigated in seeds of a number of rice cultivars belonging to the Asian rice Oryza sativa L. They were dried or ultradried to various low moisture content and then imbibed for germination testing. Few or no changes on germination percentage and vigor index were found in Indian rice seeds even after their moisture content fell to 3.5%, indicating that Indian rice exhibited a strong desiccation tolerance. On the contrary, Japonica rice seed germination percentage rapidly decreased, after their moisture content fell to 4.5%. The capacity for desiccation tolerance in Japonica (cv. Chunjiang 15) and Indian (cv. Zhongzu 1) developing seeds increased on 23–40 and 15–25 days after pollination, respectively. Though the level of monosaccharides declined, the content of sucrose has increased during desiccation. These results suggest that desiccation tolerance might be associated with the increase in seed viability and the changes in sugar level, and that raffinose could be capable of contributing to the desiccation tolerance to ultradrying. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 220–226. The text was submitted by the authors in English.     

赤霉素调控玉米种子活力的研究进展

玉米是我国总产与平均单产最高的主要农作物,对于保障国家粮食安全具有举足轻重的作用。种子活力是衡量种子质量和应用价值的关键指标,高活力种子是确保作物高产、稳产的基础。赤霉素是重要的植物生长调节物质,具有解除种子休眠、促进萌发的作用,外源赤霉素的喷施已被广泛应用于农业生产以提高作物产量。目前赤霉素对玉米种子活力的影响研究多侧重于施加外源GA影响种子活力的相关生理指标上,而赤霉素调控玉米种子活力的作用机理尚需深入研究。本文综述了赤霉素的生物合成、信号转导、作用机制以及对玉米和其他作物种子活力影响的研究进展,旨为深入探究GA对于玉米种子活力的调控机制乃至玉米育种实践中高活力玉米新种质的创制提供参考。     

On the mechanism of aging in soybean seeds

Changes in seeds of soybeans (Glycine max [L.] Merr. var. Wayne) which occur during accelerated aging (41 C, 100% relative humidity) showed subsequent loss of vigor, a decline in early respiratory activity, increased leakage of electrolytes, losses of as much as 10% dry weight from imbibing cotyledons, and a decrease in the swelling response of the imbibing system (seed plus H₂O). Each of these changes with aging is interpreted as resulting from deteriorative changes in membranes.     

Lipid-sugar interactions : relevance to anhydrous biology

The ability of seeds and other anhydrous plant forms to survive the withdrawal of water must involve a mechanism for protecting the integrity of cellular membranes. Evidence from animal systems implicates sugars as protective components, and we have tested the changes in mesomorphic phase state of phospholipid model membranes upon hydration and dehydration in the presence of sucrose and/or sucrose plus raffinose. X-ray diffraction studies of dry dimyristoylphosphatidylcholine (DMPC) indicate that the presence of sucrose lowers the chain order/disorder transition temperature to that of hydrated lipid; likewise, the lamellar repeat spacings showed the dry DMPC/sucrose mixture to be similar to that of the hydrated lipid. These results support the proposed potential of sugars to substitute for water in biomembranes. If sucrose is to serve as a protectant during desiccation of seeds, its tendency to crystallize would lessen its effectiveness. Raffinose is known to serve as an inhibitor of sucrose crystallization, and is abundant in seeds. The addition of raffinose to make DMPC/sucrose/raffinose mixtures (1/1/0.3 mass ratio) prevented sucrose crystallization, suggesting this as a possible in vivo role for raffinose.     

Galactinol synthase activity and soluble sugars in developing seeds of four soybean genotypes

Galactinol synthase (UDP-galactose:inositol galactosyltransferase) is the first unique enzyme in the biosynthetic pathway of raffinose saccharides. Its role as a regulator of carbon partitioning between sucrose and raffinose saccharides in developing soybean (Glycine max L. Merrill) seeds was examined. Galactinol synthase activity and concentrations of sucrose, stachyose, and raffinose were compared during seed development between two genotypes that were high and two genotypes that were low in mature seed raffinose saccharide concentration. In all genotypes, sucrose concentration increased as seed development progressed, but in both low raffinose saccharide genotypes, greater increases in sucrose concentration were observed late in seed development. Sucrose to stachyose ratios in mature seeds were 2.3-fold greater in low raffinose saccharide genotypes than in the high raffinose saccharide genotypes. During seed development, higher levels of galactinol synthase activity were observed in the high raffinose saccharide genotypes than in the low raffinose saccharide genotypes. A common linear relationship for all four soybean genotypes was shown to exist between galactinol formed estimated from galactinol synthase activity data and the concentration of galactose present in raffinose saccharides. Results of this study implied that galactinol synthase is an important regulator of carbon partitioning between sucrose and raffinose saccharides in developing soybean seeds.     

Changes in oligosaccharide content and antioxidant enzyme activities in developing bean seeds as related to acquisition of drying tolerance and seed quality.

Seeds of bean (Phaseolus vulgaris cv. Vernel) were collected throughout their development on the plant and dried at 15 degrees C and 75% relative humidity to a final moisture content of about 16% (fresh weight basis) to determine whether the onset of tolerance to this drying condition was related to changes in soluble sugars or the activities of the main antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Measurements of soluble sugars and enzyme activities were made after drying the seeds, and drying tolerance was evaluated by the ability of dried seeds to germinate and to produce normal seedlings. Seeds became tolerant to drying at 45 d after anthesis, a time marking physiological maturity. At physiological maturity, the moisture content of seeds was about 50-55% (fresh weight basis) and seed dry matter reached about 190 mg per seed. Seed vigour, evaluated by controlled deterioration and conductivity measurements, continued to increase after seed mass maturity, but decreased when seeds remained thereafter for more than 7 d on the plant. Acquisition of drying tolerance was coincident with an accumulation of raffinose and stachyose. Dried-tolerant seeds were also characterized by a high amount of sucrose, the most abundant sugar, and by a low content of monosaccharides. The (raffinose+stachyose)/sucrose ratio increased during seed filling, reaching a value close to 1 when all the seeds became tolerant to drying, and maintaining this proportion during the final stages of maturation. Acquisition of drying tolerance was also related to a reorientation of the enzymatic antioxidant defence system. Drying-tolerant dried seeds displayed high CAT and GR activities and low SOD and APX activities, while the opposite condition was observed in immature dried seeds. The shift in antioxidant enzymes corresponded to the beginning of the maturation-drying phase. These results suggest that oligosaccharide metabolism and enzymatic antioxidant defences may be involved in acquisition of drying tolerance during bean seed development, but are not related to seed vigour.     

Carbohydrate Changes during Maturation of Cucumber Fruit : Implications for Sugar Metabolism and Transport

Changes in the carbohydrate profiles in the mesocarp, endocarp, and seeds of maturing cucumber (Cucumis sativus, L.) fruit were analyzed. Fruit maturity was measured by a decrease in endocarp pH, which was found to correlate with a loss in peel chlorophyll and an increase in citric acid content. Concentrations of glucose and fructose (8.6-10.3 milligrams per gram fresh weight, respectively) were found to be higher than the concentration of sucrose (0.3 milligrams per gram fresh weight) in both mesocarp and endocarp tissue. Neither raffinose nor stachyose were found in these tissues. The levels of glucose and fructose in seeds decreased during development, but sucrose, raffinose, and stachyose accumulated during the late stages of maturation. Both raffinose and stachyose were found in the seeds of six lines of Cucumis sativus L. This accumulation of raffinose saccharides coincided with an increase in galactinol synthase activity in the seeds. Funiculi from maturing fruit were found to be high in sucrose concentration (4.8 milligrams per gram fresh weight) but devoid of both raffinose and stachyose. The results indicated that sucrose is the transport sugar from the peduncle to seed, and that raffinose saccharide accumulation in the seed is the result of in situ biosynthesis and not from direct vascular transport of these oligosaccharides into the seeds.     

Changes in the pool of soluble sugars induced by dehydration at the heterotrophic phase of growth of wheat seedlings

Loss of dehydration tolerance coincides with a shift from heterotrophy to autotrophy during post-germination growth of spring wheat seedlings. This critical stage falls on the fifth day following imbibition. Till the sixth day of experiment light had no effect on dry weight of the seedlings but the survival of six day old seedlings was reduced by half upon dehydration. Germinating seeds in the presence of 5 mM glucose, fructose, mannose or sucrose did not promote seedling growth but either increase (glucose, fructose) or decreased (mannose, sucrose) the survival of dehydrated seedlings. Protection against dehydration by the former sugars was correlated, irrespective of the seedling age, with the decrease of sugar pool in seeds and increase in shoots (coleoptile and first leaf) and roots. The opposite changes were provoked by the sugars hampering seedling survival. Generally, survival of wheat seedlings was not correlated with the size of soluble sugar pool but its distribution and composition. Lower mobilisation of soluble sugars in seed, lower proportion of reduced sugars to sucrose and higher share of raffinose is characteristic for the tolerant four day old seedlings and those grown in the media containing glucose or fructose. The results presented indicate that higher proportion of reduced sugars to sucrose and lower share of raffinose in six day old seedlings seems to be associated with the loss of dehydration tolerance of these seedlings, despite heterotrophic character of growth.     

盐胁迫下花生种子萌发期代谢组学分析

盐碱地高盐分会降低种子活力、抑制萌发出苗,严重制约盐碱地区花生生产和产业发展。种子萌发过程中物质代谢对种子发芽及植株形态建成至关重要,逐渐成为评价种子活力和品质的重要指标。以不同萌发期花生种子为研究对象,利用生理指标和高效液相色谱串联质谱（LC-MS/MS）分析方法,研究了盐胁迫下花生种子不同萌发期主要营养物质含量和差异代谢物的变化。种子吸水萌发促进了脂肪、蛋白质、可溶性糖代谢,随萌发时间延长,脂肪和可溶性糖含量逐渐降低,可溶性蛋白质含量呈先降后升的变化趋势。主成分分析和偏最小二乘法判别分析表明盐胁迫与对照组间代谢物差异较大,暗示盐胁迫对花生种子萌发期物质代谢影响较大。利用VIP值分析和KEGG pathway预测分析显示：正常条件下,花生种子吸水膨胀期的差异代谢物较少,未鉴定到富集的KEGG pathway;而胚根伸长期差异代谢物主要富集于12个KEGG pathway,表明萌发后期物质代谢较前期旺盛。盐处理显著提高多种差异代谢物表达水平,其中渗透保护物甜菜碱和脯氨酸差异明显;另外,盐胁迫下吸水膨胀和胚根伸长两时段的差异代谢物显著增多,分别富集到26和31个KEGG pathway。盐胁迫显著促进了能量代谢、甘油磷脂代谢、谷胱甘肽代谢以及芥子油苷生物合成途径等相关通路,推测其与盐胁迫下花生种子萌发期抗逆有关。甜菜碱和脯氨酸可能是花生种子萌发期适应盐胁迫的关键代谢物,甘油磷脂代谢、谷胱甘肽代谢以及芥子油苷生物合成等途径可能是重要的代谢调控通路。试验结果可为促进盐胁迫下花生种子萌发出苗探索新途径、新方法,以及提高盐碱地花生出苗率提供理论依据和参考价值。     

Solute Accumulation and Compartmentation during the Cold Acclimation of Puma Rye

During cold acclimation of Puma rye (Secale cereale L. cv Puma), the intracellular osmotic potential nearly doubles. During this period, the accumulation of glycinebetaine, proline, and soluble sugars was monitored. The amount of glycinebetaine increased from 290 to 1300 micrograms per gram fresh weight during the 4-week acclimation period. Proline content did not change during the first 3 weeks of acclimation but then increased from 27 to 580 micrograms per gram fresh weight during the next 3 weeks. The total soluble sugar content more than doubled by the second week of cold acclimation, increasing from 11 to 26 milligrams per gram fresh weight. Most of this increase can be attributed to the accumulation of sucrose and raffinose, whose levels increased from 2.4 and 0 to 11 and 5 milligrams per gram fresh weight, respectively. The content of monosaccharides, predominantly glucose, remained at a constant 10 milligrams per gram fresh weight throughout the acclimation period. A comparison of the sugar content of protoplasts versus vacuoles isolated from cold-acclimated leaves revealed that the extravacuolar volume contained monosaccharides, sucrose, and raffinose. Thus, the increased amounts of sucrose and raffinose that occur during cold acclimation are present in compartments external to the vacuole and may contribute to cryoprotection.     

Functional marker related to germination vigor of maize seed

Germination and synchronous seedling emergence are necessary for crop yield. One differentially expressed Cupin protein during maize seed germination had been identified in our previous study. To elucidate the functional sites in its coding gene, ZmGLP, a diverse maize association population was assayed. In alignment with B73, the ZmGLP gene contains five exons and encodes 522 amino acids, and a potential signal peptide domain from the 7 to 22 amino acids and a typical Cupin domain from the 332 to 477 amino acids were identified. The ZmGLP has a quick linkage disequilibrium decay with about 300 bp physical distance in the analyzed sequences, which implied that human selection might be undone in this gene. High genetic variations were evidenced in ZmGLP gene with 118 polymorphic sites in the association population. An Indel9 (18 bp) in the fifth exon of the intermotif region of the second Cupin domain, which influences the formation of C coil in the barrel folding, was detected significantly associated with germination vigor of maize seeds. The 18-bp insertion, which might help keeping the barrel folding intact, was a favorable allele for relative high germination vigor. Evolution analysis showed that this 18-bp deletion was a loss-of-function mutation. However, the action mode of ZmGLP is still yet to be further studied for maize improvement.     

The effect of soil drought on the composition of carbohydrates in yellow lupin seeds and triticale kernels

Carbohydrate analysis was made of yellow lupin seeds (cv. Juno) and triticale kernels (cv. Dagro), produced by plants exposed to drought stress for 21 days after the initial flowering of the first node of lupin and initial earing of triticale. The seeds of all experimental variants were harvest at full maturity, dried and stored in linen bags at 18–20 °C. Soluble carbohydrates were extracted and analysed as described by Horbowicz and Obendorf (1994). Gas chromatographic separation of carbohydrates showed that raffinose family oligosaccharides (RFO) were dominant in lupin seeds. The other carbohydrates present were sucrose (10 %), cyclitols and galactosyl cyclitols (12–13 %). Soil drought resulted in higher levels of verbascose, but decreased the quantities of the other carbohydrates in lupine seeds. In triticale kernels, over 50 % of soluble sugars were composed of sucrose and maltose, while 17.7 % were raffinose and stachyose. In response to drought the content of mono- and oligosaccharides declined. The decrease of soluble carbohydrates content in seeds of lupin and triticale kernels has no effect on the seed germination and vigour. It is assumed that the changes in the concentration of soluble sugars observed under drought may impair the storability of triticale kernels, but improve it for lupine seeds.     

An integrated overview of seed development in Arabidopsis thaliana ecotype WS

This work is part of a research program aiming at identifying and studying genes involved in Arabidopsis thaliana seed maturation. We focused here on the Wassilewskija ecotype seed development and linked physiological and biochemical data, including protein, oil, soluble sugars, starch and free amino acid measurements, to embryo development, to obtain a complete and thorough reference data set. A. thaliana seed development can be divided into three stages. During early embryogenesis (i.e. morphogenesis), seed weight and lipid content were low whereas important amounts of starch were transiently accumulated. In the second stage, or maturation phase, a rapid increase in seed dry weight was observed and storage oils and proteins were accumulated in large quantities, accounting for approximately 40% of dry matter each at the end of this stage. During the third and last stage (late maturation including acquisition of desiccation tolerance), seed dry weight remained constant while an acute loss of water took place in the seed. Storage compound synthesis ended concomitantly with sucrose, stachyose and raffinose accumulation. This study revealed the occurrence of metabolic activities such as protein synthesis, in the final phase of embryo desiccation. A striking correlation between peaks in hexose to sucrose ratio and transition phases during embryogenesis was observed.