Field mold stress induced catabolism of storage reserves in soybean seed and the resulting deterioration of seed quality in the field

Excessive rainfall provides a favorable condition for field mold infection of plants, which triggers field mold(FM) stress. If FM stress occurs during the late maturation stage of soybean seed, it negatively affects seed yield and quality. To investigate the responses of soybean seed against FM stress and identify the underlying biochemical pathways involved, a greenhouse was equipped with an artificial rain producing system to allow the induction of mold growth on soybean seed. The induced quality changes and stress responses were revealed on the levels of both transcriptome and metabolome. The results showed that soybean seeds produced under FM stress conditions had an abnormal and inferior appearance, and also contained less storage reserves, such as protein and polysaccharide. Transcriptional analysis demonstrated that genes involved in amino acid metabolism, glycolysis, tricarboxylic acid, β-oxidation of fatty acids, and isoflavone biosynthesis were induced by FM stress. These results were supported by a multiple metabolic analysis which exhibited increases in the concentrations of a variety of amino acids, sugars, organic acids, and isoflavones, as well as reductions of several fatty acids. Reprogramming of these metabolic pathways mobilized and consumed stored protein, sugar and fatty acid reserves in the soybean seed in order to meet the energy and substrate demand on the defense system, but led to deterioration of seed quality. In general, FM stress induced catabolism of storage reserves and diminished the quality of soybean seed in the field. This study provides a more profound insight into seed deterioration caused by FM stress.

THE MECHANISM OF SEED DETERIORATION

Seed deterioration is an irresistible physiological phenomenon. The aim to study seed deterioration is to see if seed deterioration can be retarded artificially and the higher seed vigor of fine varieties be maintained. The change of seed deterioration occurs in almost every system, and affects many kinds of enzyme and almost all organcllc, as a result, the seed loses its vigor. The reason of seed deterioration and the lost of seed vigor are mainly studied and discussed in this paper. According to the external and internal two kinds of theory advanced by E. H. Roberts, Much deep discussions are made from the view of biochemistry.

TaSRO1 interacts with TaVP1 to modulate seed dormancy and pre-harvest sprouting resistance in wheat

Dormancy is an adaptive trait which prevents seeds from germinating under unfavorable environmental conditions.Seeds with weak dormancy undergo pre-harvest sprouting(PHS)which decreases grain yield and quality.Understanding the genetic mechanisms that regulate seed dormancy and resistance to PHS is crucial for ensuring global food security.In this study,we illustrated the function and molecular mechanism of TaSRO1 in the regulation of seed dormancy and PHS resistance by suppressing TaVP1.The tasro1 mutants exhibited strong seed dormancy and enhanced resistance to PHS,whereas the mutants of tavp1 displayed weak dormancy.Genetic evidence has shown that TaVP1 is epistatic to TaSRO1.Biochemical evidence has shown that TaSRO1 interacts with TaVP1 and represses the transcriptional activation of the PHS resistance genes TaPHS1 and TaSdr.Furthermore,TaSRO1 undermines the synergistic activation of TaVP1 and TaABI5 in PHS resistance genes.Finally,we highlight the great potential of tasro1 alleles for breeding elite wheat cultivars that are resistant to PHS.

OsVP1 activates Sdr4 expression to control rice seed dormancy via the ABA signaling pathway

Pre-harvest sprouting(PHS)is a disadvantageous trait in cereal production worldwide,causing large economic losses each year.Its regulation mechanism is still unclear.We generated the Oryza sativa Viviparous1(OsVP1)mutant using gene editing technique,which shows increased PHS compared with that of the wild type Nipponbare.OsVP1 is localized mainly in the nucleus and expressed in various tissues and organs.Expression of Seed dormancy 4(Sdr4),a key gene controlling PHS,was sharply reduced in OsVP1 mutants.OsVP1 bound to the specific motif CACCTG in the promoter of Sdr4 and activated its expression in rice protoplasts.Overexpression of Sdr4 reduced the high seed germination rate of OsVP1 mutant cr-osvp1-1,showing that Sdr4 acts as a downstream target of OsVP1.Both OsVP1 and Sdr4 loss-of-function mutants were insensitive to exogenous ABA and employed the ABA signaling pathway in regulating seed dormancy.These findings shed light on the control of seed dormancy aimed at preventing PHS in rice.

OsbZIP09,a Unique OsbZIP Transcription Factor of Rice,Promotes Rather Than Suppresses Seed Germination by Attenuating Abscisic Acid Pathway

We successfully identified a novel and unique OsbZIP transcription factor,OsbZIP09,whose mutants exhibited longer seeds and less severe pre-harvest sprouting than the wild type,but shared similar germination rate as the wild type under normal germination conditions.The expression of OsbZIP09 was induced by abscisic acid(ABA)and declined as the germination process.As a nucleus-localized transcription factor,the conserved binding motif of OsbZIP09 was identified via DNA affinity purification sequencing technique.Further evidences indicated that OsbZIP09 directly enhanced the expression of ABA catabolism gene ABA8ox1,thus reducing ABA accumulation.In addition,OsbZIP09 also directly bound to the promoter of LEA3 gene to inhibit its expression,thus further alleviating the suppressive effect of ABA on seed germination.These results demonstrated that OsbZIP09 likely functions as a brake of the ABA pathway to attenuate the inhibitory effect of ABA on rice seed germination via dual strategies.

Influence of Water Content on the Quality of Pigeonpea Seeds

The species Cajanus cajan L. where pigeonpea is from presents a harvest potential in tropical regions for it is used as human and animal feed, besides being used as green fertilizer. However, the harvest area of this Fabaceae is still insignificant, due to especially the lack of quality seeds. In this context, it is possible to affirm that drying and store are portrayed as important steps for obtaining superior quality seeds. The aim of this study is to evaluate the physiologic quality of dwarf pigeonpea seeds, with different water content during storage. A factorial scheme 3 × 6 was adopted in the delimitation completely randomized, with four replications. Treatments were constituted by the combination of lots of seeds containing three different water contents (11%, 14% and 16%), submitted to a 10-month storage period, with evaluations every two months (0, 2, 4, 6, 8 and 10). Seeds were stocked in a bag type kraft under normal lab conditions, that is, no control. Physiologic quality of the seeds was evaluated through the following tests: Germination Pattern Test—GPT, first count of germination, accelerated aging and electric conductivity. It can be concluded that pigeonpea with hard seeds containing water content at 11% existing superior physiologic quality throughout the 10-month storage, under no controlled condition, certainly promoted by the less intense breathing from the reserves cumulated in the seed lot. Pigeonpea seeds storage with water content superior to 14% promotes a sharp decrease of physiologic quality, due to an increase in metabolic activity.

Physiological Differences Between Yellow-Seeded and Black-Seeded Rapeseeds (Brassica napus L.) with Different Testa Characteristics During Artificial Ageing

Yellow-seeded rapeseed (Brassica napus L.) is a new kind of breeding resources with yellow color, increased oil and protein content and less unwanted crude fiber content due to the thinner and transparent testa compared with traditional black or brown-seeded rapeseed. To analyze the longevity of the yellow-seeded rapeseed during storage, the physiological differences between the yellow and black-seeded near-isogenic lines were studied by artificial ageing method. The testa rate, anthocyanin content and melanin content of yellow-seeded rapeseeds decreased by 20.1, 25.2, and 80.4% respectively than black-seeded rapeseed. During artificial ageing, the yellow-seeded rapeseed showed significantly different effect of ageing compared with the black-seeded, as demonstrated by faster deterioration with lower germination percentage, seed vigour index, reducing sugar and soluble protein contents than the black-seeded, as well as a drastic increase in electrical conductivity, malnodialdehyde (MDA) content and a rapid decrease in activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). The results suggested that the transparent testa of the yellow-seeded rapeseed lost some abilities to protect the embryo against adverse environmental conditions and thus led to a poor storability.

Physiological Quality of Pigeonpea Seed after Application of Desiccant Herbicides

The pre-harvest application of herbicides may impair seed quality. This way, this paper was conducted to evaluate the effects of the application of desiccant herbicides on the physiological quality of pigeonpea seeds. Six batches of seeds from plants desiccated with glyphosate were evaluated at doses: 1.125 (B1), 1.5 (B2) and 1.875 L&middotha-1 (B3);and Gramocil (20% Paraquat + 10% Diurom) at doses: 1.5 (B4) and 2 L&middotha-1 (B5), and a control which received no application (B6). Seed viability was assessed through the germination standard test, and vigor through the first germination count, accelerated aging, electrical conductivity, seedling length, seedling dry matter and biomass density tests. The experimental design was the completely randomized, with four replications. Data were submitted to variance analysis, and when significant effects were observed, the Scott- Knott test was carried out at 5% probability using the SISVAR 5.1 software. The results showed that: a) the application of 1.875 L&middotha-1 of glyphosate was harmful to pigeonpea seed viability and vigor, evaluated through the accelerated aging test;b) applications of glyphosate in a 1.875 L&middotha-1 dose and Gramocil in 2 L&middotha-1 resulted in low vigor according to the electrical conductivity test of seeds;and c) the seed vigor measured by the first count, seedling length, seedling dry matter and biomass density test was not influenced by the type of desiccant applied.

紫花苜蓿种子对逆境贮藏条件的反应

以陇东紫花苜蓿 (MedicagosativaL .cv .“Longdong”)种子为材料 ,在室温、35℃和 35℃ +10 %的种子含水量 (SMC) 3种贮藏、接种或不接种燕麦镰刀菌 (Fusariumavenaceum (Fr.)Sacc .)的条件下 ,1年贮藏期内对各逆境处理的种子每隔 6 0d进行 1次标准发芽试验 ,2 0℃恒温、第 10d统计种子的发芽率和死亡率 ,试验结束时计测种子幼苗的长度和感病率 ;在大田条件下观测各处理种子的出苗率 ,确定催腐 (CD)与各种贮藏条件下的苜蓿种带真菌种类和检出率 .结果表明 ,随着贮藏温度和种子含水量等逆境贮藏条件胁迫的加剧 ,苜蓿种带真菌检出率逐渐增高 ,从室温、35℃条件下的 10 %上升到CD +35℃ +10 %SMC条件下的 2 9% ;抗病性逐渐减弱 ,35℃ +10 %SMC条件下幼苗的感病率和种子死亡率显著 (P <0 .0 5 )高于室温和 35℃下的感病率和种子死亡率 ;室内种子发芽率和田间出苗率逐渐下降 ,35℃ +10 %SMC条件下的种子的发芽率和田间出苗率显著 (P <0 .0 5 )低于在室温和 35℃下的发芽率和田间出苗率 ;幼苗生长受到抑制 ,35℃ +10 %SMC条件下的苗长和根长显著 (P <0 .0 5 )低于在室温和 35℃下的幼苗长度 .随着贮藏时间的延长 ,种子真菌检出率和田间出苗率下降 ,幼苗感病率增加 .与未接种的对照相比 。

春大豆种子田间劣变性和劣变抗性的差异蛋白质组学研究

【目的】南方春大豆种子在生理成熟(R6或R7期)过程中易受高温高湿胁迫影响常会发生种子田间劣变,已经严重制约了中国南方春大豆生产和应用的发展。应用比较蛋白质组学技术,在蛋白表达水平上揭示高温高湿下南方春大豆种子田间劣变性和劣变抗性的机制,为遗传育种改良和新品种选育奠定种质基础。【方法】利用抗种子田间劣变种质湘豆3号和不抗种质宁镇1号为材料,在种子发育到生理成熟期时模拟田间高温高湿胁迫处理,运用双向电泳(2-DE)和MALDI-TOF/TOF鉴定技术研究春大豆种子蛋白质表达谱的变化。【结果】高温高湿胁迫处理和对照条件下(1、5、10、16和24 h),湘豆3号和宁镇1号大豆种子可溶性蛋白的每张2-DE重复胶上都可以检测到700多个可重复蛋白点,50个蛋白质点在处理与对照之间表达量上存在显著差异。其中有33个差异蛋白点经质谱分析成功鉴定;功能分类表明,这些成功鉴定的差异蛋白分别涉及细胞修复及防御(9%)、氧化还原平衡(12%)、蛋白合成(3%)、能量代谢(15%)、转运过程(15%)以及贮藏蛋白(31%)等代谢途径和细胞过程。此外,还有5个差异蛋白为未知功能蛋白。【结论】高温高湿胁迫下,抗性种质湘豆3号较不抗种质宁镇1号具有较强的抗氧化和细胞修复及防御能力,可能是其具有较强的抗种子田间劣变性的关键原因。

贮藏温度对不同含水量老芒麦种子生理特性的影响

试验以不同含水量(4%,10%,16%,22%,28%,34%,40%)老芒麦种子为材料,研究贮藏温度对老芒麦种子氧自由基、抗氧化酶及膜脂过氧化程度的影响,为探索种子劣变的内在机制奠定基础。结果表明,经过4℃低温和常温贮藏后,种子发芽率不同程度降低,含水量高的种子发芽率下降明显;随着含水量增加,死种子明显增多,超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量总体呈下降趋势。在低温贮藏条件下,抗坏血酸过氧化物酶(APX)活性、O2.-产生速率随含水量的升高不断下降,在含水量达到28%时,APX活性、O2.-产生速率开始上升。在常温贮藏条件下,种子含水量在22%之后,APX活性升高,O2.-产生速率总体呈下降趋势,但含水量在16%时,O2.-产生速率突然升高,发芽率降低到0%,不正常、新鲜未发芽种子和死种子明显增多。在低水分(4%～16%)条件下,超氧阴离子自由基的积累可能是引起种子劣变的关键,而高含水量种子的活力下降,并非与自由基积累及脂质过氧化作用相关。

新麦草种子劣变过程中生理生化变化

研究新麦草(P sa thy rostachy s juncea Bozo isky)种子在自然老化和人工老化过程中的生理生化变化。结果表明:在自然和人工老化过程中,种子发芽率、发芽指数、脱氢酶和酸性磷酸酯酶活性降低;发芽指数和酸性磷酸酯酶活性的变化先于发芽率,这是种子质量的敏感指标;种子可溶性糖泄漏随着老化程度的增加而增加;电导率与种子劣变程度的相关不显著。

种子劣变的生理学研究进展综述

作者综述了近１５年来国内外种子劣变生理学的研究进展，重点概括了种子劣变的生理变化与模式，并提出今后在该研究领域应关注的问题。

人工老化处理对结球甘蓝种子生理生化特性的影响

以结球甘蓝品种‘冬升’种子为材料,研究高温(40℃)高湿(相对湿度100%)人工老化处理过程中种子的萌发特性、种子浸出液相对电导率和丙二醛、可溶性蛋白、可溶性糖含量以及抗氧化酶活性的变化,以揭示种子劣变的机理。结果表明:(1)人工老化处理甘蓝种子的含水量和不正常苗率均随着老化时间的延长逐渐增加,而种子发芽势、发芽率、发芽指数和活力指数的增加均逐渐降低。(2)随着处理天数的延长,老化处理甘蓝种子的浸出液电导率显著增大,浸出液可溶性糖含量逐渐升高,可溶性蛋白含量表现出显著下降趋势,而种子MDA含量呈先升高后逐渐下降的趋势。(3)在结球甘蓝种子老化进程中,其种子中SOD、POD、CAT活性变化的趋势相似,均随老化程度的加深而逐渐降低;而APX活性在老化处理的最初2d显著增加,第6天显著降低。研究发现,在结球甘蓝种子老化进程中,种子活力和萌发率显著降低,其种子浸出液电导率、可溶性蛋白含量、可溶性糖含量、保护酶活性变化与种子老化及劣变程度密切相关,膜脂过氧化作用可能是引起或加剧种子老化劣变的重要原因之一。

数种牧草种子劣变的生活力与膜透性的关系

以3种豆科和2种禾本科牧草包括紫花苜蓿、光叶紫花苕、沙打旺、苏丹草和老芒麦为材料,研究了种子劣变过程中生活力与水浸电导率的关系。结果表明3种豆科种子的生活力(x)与水浸电导率(y)皆呈极显著负相关(P<0.01)。可用如下回归方程表示:紫花苜蓿:y=-1.866x+288.56(r=-0.982);光叶紫花苕:y=-1.099x+194.20(r=-0.902);沙打旺:y=-1.889x+308.22(r=-0.983)。然而,2种禾本科种子生活力却与电导率不相关(P>0.05),而且电导率的测定值甚小。种子吸水实验证明禾本科与豆科种子在24h内的不同吸水阶段皆表现为高生活力的吸水率显著低于低生活力种子(P<0.01)。

春大豆种子劣变的研究

用不同地理来源的９个春大豆品种，进行了两年春，秋两季播种，及播期与收获时期试验，研究种子劣变过程及其影响因素。结果显示：春大豆种子的劣变，收获前劣变起主导作用，高温高湿气候影响种子发育则为主要原因。收获前种子劣变并非真菌感染所致。播季间，播期间及收获时间不同，种子劣变差异显著，春播提早播种及秋播是获得高活力种子的途径。收获后种子劣变与贮藏条件有关，高温高湿加速劣变。干燥，密闭贮藏能减轻种子劣变速度，短期贮藏（９个月以内）减轻效果不显著，随贮藏时间延长（１２个月以上）则干燥贮藏显著减缓种子劣变。本文同时对种子劣变过程与生产高质量种子以及抗性遗传育种作了探讨。

油菜种子老化处理后的生理生化变化

以油菜品种‘镇油6号′种子为材料,研究油菜种子在高温(50℃)高湿(相对湿度100%)老化处理后的萌发特性、种子浸出液相对电导率、丙二醛、可溶性蛋白和可溶性糖含量以及抗氧化酶活性的变化。结果表明,随着老化时间的增加,油菜种子的发芽势、发芽率、发芽指数及其活力指数均显著降低。同时,随着老化天数的延长,浸出液电导率显著性增大,浸出液可溶性糖含量则逐渐升高;可溶性蛋白含量表现出下降趋势;种子MDA含量呈现先升高后逐渐下降的趋势。此外,在油菜种子老化进程中,SOD、POD、CAT活性变化的趋势基本一致,其活性均随老化天数的延长而逐渐降低;研究发现,在油菜种子老化处理中,种子浸出液电导率、可溶性蛋白含量和可溶性糖含量与种子老化及劣变程度显著性相关;膜脂过氧化作用也可能是引起或加剧种子老化劣变的重要原因之一。

蓝茎冰草种子劣变过程中生理生化变化

研究蓝茎冰草(Pascopyrum smithii)种子在自然和人工老化过程中生理生化变化。结果表明:在自然和人工老化过程中,发芽率和活力指数下降,活力指数的变化先于发芽率,是反映种子质量的敏感指标;蓝茎冰草种子电导率与种子生活力及活力正相关;氨基酸泄漏与种子中游离氨基酸含量正相关,不反映种子膜的透性;蓝茎冰草种子中可溶性蛋白质含量随着人工老化而上升。

大白菜种子人工老化及劣变的生理生化分析

研究了大白菜种子人工老化过程中所发生的一系列生理生化变化。结果表明：随着种子老化加深， 种子活力指数、ＰＯＤ、ＳＯＤ、脱氢酶、酸性磷酸酶、脂肪酶活性逐渐降低， ＭＤＡ 及芥子碱含量逐渐增加， 且品种间有差异。认为大白菜种子人工老化及劣变的主要机制在于膜脂过氧化作用加剧。

辣椒种子人工老化及劣变的生理生化变化

为了探明辣椒种子活力下降的原因和一些生理生化变化规律,采用人工加速老化方法,研究了辣椒种子人工老化过程中所发生的一系列生理生化变化.结果表明:随着种子老化加深,发芽势、发芽率、活力指数、过氧化物酶、超氧化物歧化酶活性和可溶性糖、可溶性蛋白质含量逐渐降低,相对电导率和MDA含量不断增加,且品种间有差异.而脱氢酶活性在不同老化程度种子间无明显差异.认为辣椒种子人工老化及劣变的主要机制在于膜脂过氧化作用加剧.