Genetic variation for seed phosphorus and yield traits in Indian sorghum landraces and varieties

Phytic acid is the major storage form of phosphorus in cereals. It binds with nutritionally important metals and affects mineral bioavailability. The present study analyzed phytic acid, inorganic phosphorus(IP) content, seed weight, and grain yield in 98 sorghum landraces and varieties grown in two environments to evaluate genotypic and environmental effects and to determine trait stability. Genotypic effects and genotype × interaction were significant for phytic acid concentration and yield components. A promising landrace, Malkhed-1, had the lowest phytic acid(0.015 mg g-1)concentration, with a higher yield(70.02 g plant-1), than the check variety M-35-1 in both environments. Similarly, among the varieties, Phule Maulee showed the lowest phytic acid(0.07 mg g-1) and a higher grain yield of 53.15 g plant-1in both environments. Phytic acid and IP were negatively correlated(r =- 0.34), whereas grain yield and seed weight were positively correlated(r = 0.20). Cluster analysis based on seed phosphorus traits and yield components identified five and six clusters, respectively. Genotypes containing low phytic acid with high yield identified in this study would be helpful for increasing the bioavailability of mineral nutrients.     

Quinclorac Resistance in Echinochloa crus-galli from China

Echinochloa crus-galli is a major weed in rice fields in China, and quinclorac has been long used for its control. Over-reliance of quinclorac has resulted in quinclorac resistance in E. crus-galli. Two resistant(R) E. crus-galli populations from Hunan, China were confirmed to be at least 78-fold more resistant to quinclorac than the susceptible(S) population. No difference in foliar uptake of 14 C-labelled quinclorac was detected between the R and S plants. However, a higher level of 14 C translocation and a lower level of quinclorac metabolism were found in the R plants. Basal and induced expression levels of β-cyanoalanine synthase(β-CAS) gene and β-CAS activity were not significantly different between the R and S plants. However, the induction expression of 1-aminocyclopropane-1-carboxylic acid oxidase(ACO1) gene by quinclorac treatment was evident in the S plants but not in the R plants. Quinclorac resistance in the two resistant E. crus-galli populations was not likely to be related to foliar uptake, translocation or metabolism of quinclorac, nor to cyanide detoxification via β-CAS. Thus, target-site based quinclorac signal reception and transduction and regulation of the ethylene synthesis pathway should be the focus for further research.     

Flower Development and Photoperiodic Control of Flowering in Rice

Floral transition,which is referred to as a plant’s transition from vegetative stage to reproductive stage,is considered to be a critical developmental switch in higher plants,for a timely flowering is a major factor of reproductive success.Endogenous and environmental cues,such as photoperiod,light quality,plant hormones concentrations and temperature,provide information to the plants whether the environment is favorable for flowering.These cues promote,or prevent,flowering through a complex genetic network,mediated by a careful orchestration of temporal and spatial gene expression.One of such cues is photoperiod.Rice(Oryza sativa L.) serves as a powerful model species for the understanding of flowering in higher plants,including flower development and photoperiodic control of flowering.In this review,we overviewed and discussed the flower development and its model.We also overviewed the photoperiodic pathways in rice flowering control,and summarized the pathways at molecular level.     

Effect of Nitrogen on Water Content, Sap Flow, and Tolerance of Rice Plants to Brown Planthopper, Nilaparvata lugens

Water content (WC) and sap flow from leaf sheath of rice plants with varying nitrogen levels at different growth stages, and fluctuations in relative water content (RWC) of rice plants being damaged by brown planthoppcr (BPH), Nilaparvata lugens were determined in the laboratory, and the tolerance of rice plants to BPH at different nitrogen regimes was evaluated in the greenhouse at International Rice Research Institute (IRRI), the Philippines. The results indicated that both WC and RWC were increased significantly, as the amount of sap flow from rice plants was reduced statistically, with the increase of nitrogen content in rice plants. RWC in rice plants applied with high nitrogen fertilizer decreased drastically by the injury of BPH nymphs, while the reduced survival duration of rice plants with the increase of nitrogen content was recorded. These may be considered to be one of the important factors in increasing the susceptibility to BPH damage on rice plants applied with nitrogen fertilizer.     

Chromosome Number Manipulation as Part of Potato Pre-breeding Programs

The cultivated potato(Solanum tuberosum L.) is a tetraploid(2n=4x=48) and can be improved with the incorporation of desirable traits from other Solanum species.Often the transfer of these traits is hindered by complex genetics and breeding barriers within potato.Parthenogenesis and microsporogenesis are used in chromosome number manipulation allowing breeders to reduce the potato's chromosome number to dihaploid(2n=2x=24)[diploid] or monohaploid(2n=x=12) from which a predictable transfer of traits can be made,in accordance with the endosperm balance number theory(EBN).Furthermore,the reproductive processes of first division restitution(FDR) and second division restitution(SDR) are utilized in order to increase the chromosome number for incorporation into the cultivated potato.     

Natural Colonization of Rice by Arbuscular Mycorrhizal Fungi in Different Production Areas

Interactions between plants and soil microorganisms can influence the other interactions in which plants participate, including interactions with herbivores. Many fungi, including arbuscular mycorrhizal fungi(AMF), form symbiotic relationships with the roots they inhabit, and potentially alter defense against pests. The objective of this study was to document the extent of root colonization by AMF on non-flooded rice plants grown under conditions typical of commercial fields. We hypothesized that AMF naturally colonized rice plants in different rice producing field locations. Rice plant samples were collected from areas across the southern United States, including Texas, Mississippi, Arkansas and two research stations in Louisiana. We quantified the amount of AMF colonization in insecticide-free rice plants over three consecutive years(2014–2016). The results revealed natural colonization of AMF in all rice producing areas. In all the three years of survey, rice-AMF associations were the greatest in Arkansas followed by Mississippi and Texas. This research will help draw attention to natural colonization of AMF in rice producing areas that can impact future rice research and production by facilitating agricultural exploitation of the symbiosis.     

WRKY72 Negatively Regulates Seed Germination Through Interfering Gibberellin Pathway in Rice

Seed germination is associated with grain yield and quality in crop production.Gibberellic acid(GA)serves as a major phytohormone in the promotion of seed germination.It is synthesized in the embryos and transmitted to the aleurone layers,where GA triggers the synthesis and secretion of a set of hydrolases,especiallyα-amylase.Subsequently,the storage nutrients such as starch in the endosperm are digested by these hydrolases and absorbed by the embryo to sustain seed germination and early seedling establishment(Kaneko et al,2002).The detailed GA biosynthesis process has been well studied and thoroughly reviewed in several literatures(Sakamoto et al,2004;Reinecke et al,2013).Briefly,geranylgeranyl diphosphate(GGDP)is turned into ent-kaurene by two terpene synthases,ent-copalyl diphosphate synthase(CPS)and ent-kaurene synthase(KS).Subsequently,the conversion of GA precursor ent-kaurene to ent-kaurenoic acid is catalyzed by ent-kaurene oxidase(KO),and that from ent-kaurenoic acid to GA12 is catalyzed by ent-kaurenoic acid oxidase(KAO).Ultimately,GA12 is converted to various GA intermediates and bioactive GAs by GA20-oxidase(GA20ox)and GA3-oxidase(GA3ox),respectively.     

Rice gene OsUGT75A regulates seedling emergence under deep-sowing conditions

Poor seedling emergence is a challenge for direct seeding of rice under deep-sowing field conditions. Here we reveal that UDP-glucosyltransferase OsUGT75A promotes rice seedling emergence under deepsowing conditions by increasing shoot length. Expression of OsUGT75A was higher in the middle regions of the shoot and in shoots under deep-sowing conditions. Levels of free abscisic acid(ABA) and jasmonates(JA) were higher in shoots of OsUGT75A mutants than in those of wild-type plants, and OsUGT75A ...     

转基因水稻中重组植酸酶的表达

为通过在转基因植株中表达植酸酶降解植酸来提高水稻中无机磷利用率,构建了由玉米泛素基因Ubi启动子控制的植酸酶基因植物表达载体,并以来源于水稻未成熟胚的愈伤组织作为转化受体,经农杆菌介导法将植酸酶基因导入水稻中,共获得15个独立的转基因株系。对转基因水稻总DNA的PCR和Southern 杂交分析证明目的基因已整合入转基因水稻植株基因组中,并能稳定遗传。对部分转基因水稻未成熟种子总RNA进行RT PCR分析,表明导入的植酸酶基因能够在转基因水稻种子中正常表达。无机磷含量分析表明含目的基因的转基因水稻种子及其后代叶片中的无机磷含量较未转化植株均有了明显的提高。     

转磷酸甘露糖变位酶基因提高水稻维生素C含量

维生素C(VC)是人体健康所必需的营养元素。人类由于缺乏VC合成途径中的最后一种酶(L-古洛糖酸内酯氧化酶),自身不能合成VC。水稻是重要的粮食作物,增加水稻种子中VC含量,能够提高其营养价值。磷酸甘露糖变位酶(PMM)是VC合成通路中一种重要的酶,催化甘露糖-6-磷酸到甘露糖-1-磷酸的转变。将水稻PMM基因(OsPMM)构建在双右边界双元载体pMNDRBBin6上,并用种子特异表达的启动子BX14驱动其表达。通过农杆菌介导的转化系统,OsPMM基因被转入粳型三系恢复系C418中。通过分子检测,在T_2代筛选到了无选择标记的转基因植株。对OsPMM基因在转基因植株中的表达进行分析,发现OsPMM基因在转基因水稻种子内的表达水平明显提高,相应地,转基因系种子中的VC含量也提高了25%~50%。     

水稻转录因子基因OsPHR3在磷素利用过程中的作用

磷是植物体生长发育所必需的大量营养元素之一,广泛参与植物体多种生命活动。土壤中磷的有效性很低,是农业生产中限制作物产量的重要因素。OsPHR3(LOC_Os02g04640)属于MYB-CC家族,与水稻中磷信号途径中心调控因子OsPHR2是同源基因,且具有部分功能重叠。本研究利用转基因技术获得OsPHR3基因的突变体和超表达材料,通过水培实验、~(32)Pi同位素实验以及桶培实验来研究该基因在吸收利用磷素过程中的作用。水培实验表明,与野生型相比,突变体磷含量无明显差异,基因超表达能够提高水稻体内磷含量。~(32)Pi同位素实验显示,与野生型相比,缺磷时突变体吸收速率降低,而该基因超表达能够促进磷素的吸收与转运。桶培实验表明,该基因超表达能够增加水稻有效分蘖数,提高种子中磷含量,该基因缺失使得穗长变短。OsPHR3基因可能调控促进磷的吸收与向地上部转运。该研究将为以后分子育种提供依据。     

外源木聚糖酶基因atx在水稻中的表达

 为通过在转基因植株中表达木聚糖酶来提高木聚糖酶的生产效率,将具有较高热稳定性和催化活性的杂合木聚糖酶基因atx连接到双元表达载体pCAMBIA1301上,成功构建了木聚糖酶植物表达载体atx Ru3ep 1301。然后以水稻成熟胚的愈伤组织作为转化受体,采用农杆菌介导法将木聚糖酶基因导入水稻(中花11)中。经过潮霉素抗性检测和PCR鉴定,证实目的基因已经整合到转基因水稻基因组中。RT PCR分析结果显示,外源木聚糖酶基因能够在CaMV 35S启动子的引导下在转基因水稻中正常转录。转基因水稻能够正常生长和繁殖。木聚糖酶活性分析表明,转基因植株最高木聚糖酶活性约为4.37 U/g（鲜叶片）。因此,利用转基因水稻生产木聚糖酶将会是一种经济、有效的方法。     

额种子蛋白体靶向表达口服重组胰岛素原载体构建及转化水稻

应用水稻种子生物反应器开发口服重组胰岛素原具有重要应用前景。通过分子设计保证重组胰岛素原在人体肠道内的自主加工成熟,根据水稻密码子偏爱性人工合成了霍乱毒素β亚基和人胰岛素原的融合基因(cholera toxin B subunit fused with human proinsulin,CTBIN),并在C末端添加内质网滞留信号KDEL。通过PCR技术从粳稻品种日本晴全基因组中克隆谷蛋白启动子及其信号肽序列pGluB1sig(GluB1 promoter and its signal peptide)用于驱动融合基因CTBIN的表达,插入载体pCAMBIA1302,构建了水稻种子蛋白体靶向表达口服重组胰岛素原的载体pCAMBIA1302-pGluB1sig-CTBIN-Nos。采用农杆菌介导法转化日本晴,获得了46株转基因水稻植株,Western杂交检测到CTB-人胰岛素原融合蛋白在水稻种子中表达。     

水稻种胚LOX3基因在逆境胁迫中的作用

LOX3是主要的水稻种胚脂氧合酶同工酶。为了研究水稻LOX3基因在逆境胁迫中的作用,构建了LOX3基因的反义植物表达载体,用农杆菌介导法转化水稻品种武运粳7号和Kasalath,获得了转基因植株。PCR和Southern鉴定证实基因已经导入水稻基因组中,种胚LOX3缺失鉴定和半定量RT PCR分析证实反义RNA抑制了LOX3基因的表达。对T2代转基因植株进行了水分胁迫处理及稻瘟病和白叶枯病的接种鉴定。结果显示,与非转基因对照相比,反义LOX3转基因植株对水分胁迫、稻瘟病和白叶枯病都表现敏感,说明水稻种胚LOX3基因在逆境胁迫反应中发挥一定的作用。     

Quality characteristics and field performance of selectable marker-free transgenic rice with antisense Wx gene and improved quality derived from the elite parents of hybrid indica rice

In rice grains, high amylose content (AC) is correlated with poor grain quality, particularly in indica hybrid rice. To obtain indica hybrid rice with improved cooking and eating qualities, we introduced the antisense Waxy (Wx) gene into 2 elite parental lines of indica hybrid rice by using co-transformation methods. Subsequently, we selected several elite homozygous transgenic lines that did not contain the selectable marker. The expression of the endogenous Wx gene of the selected transgenic lines was significantly downregulated, resulting in low AC in the mature seeds; moreover, the AC in some lines reduced to the level observed in glutinous rice. With the decrease in AC, the gel consistency of the transgenic rice became softer, and the gelatinization temperature tended to be higher than those of the wild types, especially in the case of the Longtefu-derived transformants. We also analyzed the pasting properties of the selected transgenic low-AC lines, and we noted an improvement in the pasting properties of the transgenic rice lines. The results from a field trial indicated that the grain weights of the transgenic lines with lower AC exhibit remarkable reduction compared with those of the wild types.     

Role of LOX3 Gene in Alleviating Adverse Effects of Drought and Pathogens in Rice

Lipoxygenase 3 (LOX3) is a major component of the LOX isozymes in mature rice seeds. To investigate the role of LOX3 gene under stresses, a plant expression vector containing antisense cDNA of LOX3 was constructed. Rice varieties Wuyunjing 7 and Kasalath were transformed by the Agrobacterium-mediated method and transgenic rice plants were generated. PCR and Southern blot results showed that the antisense LOX3 gene was integrated into the rice genome. Analyses of embryo LOX3 deletion and semi-quantitative RT-PCR confirmed the antisense suppression of LOX3 gene in transgenic plants. The T2 antisense plants of LOX3 were sensitive to drought stress, rice blast and bacterial blight compared with non-transgenic plants. These results suggest that the LOX3 gene might function in response to stresses.     

Quality characteristics and field performance of selectable marker-free transgenic rice with antisense Wx gene and improved quality derived from the elite parents of hybrid indica rice

In rice grains, high amylose content (AC) is correlated with poor grain quality, particularly in indica hybrid rice. To obtain indica hybrid rice with improved cooking and eating qualities, we introduced the antisense Waxy (Wx) gene into 2 elite parental lines of indica hybrid rice by using co-transformation methods. Subsequently, we selected several elite homozygous transgenic lines that did not contain the selectable marker. The expression of the endogenous Wx gene of the selected transgenic lines was significantly downregulated, resulting in low AC in the mature seeds; moreover, the AC in some lines reduced to the level observed in glutinous rice. With the decrease in AC, the gel consistency of the transgenic rice became softer, and the gelatinization temperature tended to be higher than those of the wild types, especially in the case of the Longtefu-derived transformants. We also analyzed the pasting properties of the selected transgenic low-AC lines, and we noted an improvement in the pasting properties of the transgenic rice lines. The results from a field trial indicated that the grain weights of the transgenic lines with lower AC exhibit remarkable reduction compared with those of the wild types.     

低磷条件下过表达OsPHF1基因对粳稻农艺性状的影响

【目的】 磷酸盐转运体运输协助因子(PHF1)通过转录后调节特定磷转运蛋白,影响磷酸盐的利用效率。本研究通过培育过表达OsPHF1的无选择标记转基因粳稻空育131,研究在不同磷浓度环境中OsPHF1的过表达对粳稻空育131产量的影响,为培育可商品化的磷高效转基因水稻品种提供依据。方法 利用双T-DNA方法构建OsPHF1的过表达载体,通过农杆菌侵染法和后续筛选获得了无选择标记的转基因空育131纯合株系,通过对T₃和T₄代转基因植株的田间试验,研究转基因品系在低磷浓度(75或112.5 kg/hm²过磷酸钙)、中低磷浓度(225或300 kg/hm²过磷酸钙)和正常磷浓度(450 kg/hm²过磷酸钙)下的农艺性状。结果 获得了3个无筛选标记的纯合OsPHF1过表达转基因空育131株系F18-18、F22-32和F25-6。其中,F22-32和F25-6的OsPHF1的表达量远高于野生型。大田试验显示,F22-32和F25-6株系的T₃代在中低磷(300 kg/hm²过磷酸钙)环境中,分蘖数比对照分别增加了55%和25%,增产幅度分别为38%和34%;F22-32和F25-6株系T₄代在低磷条件下(112.5 kg/hm²过磷酸钙)产量的增幅最大,增产了30%~35%;在中低磷条件下(225 kg/hm²过磷酸钙)分蘖数和产量也有明显增加。结论 双T-DNA法能用于培育过表达OsPHF1的无筛选标记转基因水稻。田间试验显示,高表达OsPHF1的转基因株系在中低磷条件下(112.5、225或300 kg/hm²过磷酸钙)分蘖数和产量稳定增加。