绿豆基因组研究进展

绿豆是亚洲国家重要的经济作物。绿豆基因组的研究工作已开展多年,至今已经发布了6张遗传连锁图谱,然而还未有一张图谱的连锁群数与绿豆(2n=2x=22,n=11)的染色体基数一致。近年来,豆科植物比较基因组学的研究成果,为绿豆遗传连锁图谱的发展提供了新的思路。通过将绿豆遗传连锁图与其他豆类连锁图比较发现,绿豆与小豆、豇豆、普通菜豆、大豆、藊豆以及豆科模式植物—蒺藜苜蓿的基因组间有不同程度的保守性,其中尤以绿豆与普通菜豆基因组间共线性水平高。本文分别从绿豆遗传连锁图谱构建、比较基因组作图以及抗豆象基因定位等方面进行了综述,以期为绿豆遗传研究工作者提供参考。     

Segregation distortion for seed testa color in Mungbean (Vigna radiata L. Wilcek)

Genetic segregation experiments with plant species are commonly used for understanding the inheritance of traits. A basic assumption in these experiments is that each gamete developed from megasporogenesis has an equal chance of fusing with a gamete developed from microsporogenesis, and every zygote formed has an equal chance of survival. If gametic and/or zygotic selection occurs whereby certain gametes or zygotic combinations have a reduced chance of survival, progeny distributions are skewed and are said to exhibit segregation distortion. In this study, inheritance data are presented for the trait seed testa color segregating in large populations (more than 200 individuals) derived from closely related mungbean (Vigna radiata L. Wilcek) taxa. Segregation ratios suggested complex inheritance, including dominant and recessive epistasis. However, this genetic model was rejected in favor of a single-gene model based on evidence of segregation distortion provided by molecular marker data. The segregation distortion occurred after each generation of self-pollination from F1 thru F7 resulting in F7 phenotypic frequencies of 151:56 instead of the expected 103.5:103.5. This study highlights the value of molecular markers for understanding the inheritance of a simply inherited trait influenced by segregation distortion.     

Simple and Effective Regeneration of Mungbean (Vigna radiata (L) Wilczek) using Cotyledonary Node Explants

Mungbean (Vigna radiata (L) Wilczek cv ML — 267) is a recalcitrant grain legume species. Direct multiple shoots were developed from the cotyledonary node explants of 2-day-old in vitro grown seedlings of mungbean. Maximum number of shoots (an average 12.1 shoots per explant) was obtained on a medium containing MS salts, B5 vitamins and 5.0 mg l^?1 BAP. A medium with lower BAP concentration appeared suitable for rapid shoot elongation. The elongated shoots were rooted on 0.2 mg l^?1 NAA. The rooted plants were acclimatized under field conditions. The survival of the plants in the greenhouse was 90 %. Plants flowered and set seed normally.     

Callus Induction from Mesophyll and Hypocotyl Protoplasts of Mungbean (Vigna radiata (L))

Mesophyll and hypocotyl protoplasts were isolated from Vignaradiata using a combination of Cellulase Onozuka RIO (1%) andMacerozyme (0·2%). On a modified V-47 medium, 60% ofthe cultured protoplasts divided and developed into colonies.Protoclones differentiated roots on MS medium supplemented withdifferent auxins and cytokinins; however, shoot differentiationwas not obtained. Co-cultivation of protoplasts with wild andshooter mutants of Agrobacterium tumefaciens did not lead todifferentiation of plantlets. Lysopine and nopaline dehydrogenasewere not detected in any of the selected protoclones. Vigna radiata, Mungbean, Agrobacterium tumefaciens, co-cultivation, protoplasts     

分子标记在绿豆遗传连锁图谱构建和基因定位研究中的应用

绿豆(Vigna radiata(L.)Wilczek)作为一种医食两用作物,不仅是重要的食物资源,在改善土壤环境、提高农民收入等方面也发挥着重要作用。然而,相对于大宗作物而言,绿豆基础研究薄弱,基因组研究更是落后。近年来,分子标记技术迅速发展,在绿豆基因组学研究中发挥了重要的作用。国内外利用分子标记技术已构建了超过20张绿豆遗传连锁图谱。一些优良基因尤其是与抗性相关的基因被鉴定或精细定位,为绿豆分子标记辅助选择打下基础,加快了抗性新品种的培育进程。本研究通过对分子标记技术在绿豆遗传连锁图谱构建、重要功能基因的定位等方面的应用进行综述,以期为绿豆遗传育种研究及功能基因组学分析提供参考。     

Construction of a Genetic Linkage Map and Genetic Analysis of Domestication Related Traits in Mungbean (Vigna radiata)

The genetic differences between mungbean and its presumed wild ancestor were analyzed for domestication related traits by QTL mapping. A genetic linkage map of mungbean was constructed using 430 SSR and EST-SSR markers from mungbean and its related species, and all these markers were mapped onto 11 linkage groups spanning a total of 727.6 cM. The present mungbean map is the first map where the number of linkage groups coincided with the haploid chromosome number of mungbean. In total 105 QTLs and genes for 38 domestication related traits were identified. Compared with the situation in other Vigna crops, many linkage groups have played an important role in the domestication of mungbean. In particular the QTLs with high contribution were distributed on seven out of 11 linkage groups. In addition, a large number of QTLs with small contribution were found. The accumulation of many mutations with large and/or small contribution has contributed to the differentiation between wild and cultivated mungbean. The useful QTLs for seed size, pod dehiscence and pod maturity that have not been found in other Asian Vigna species were identified in mungbean, and these QTLs may play the important role as new gene resources for other Asian Vigna species. The results provide the foundation that will be useful for improvement of mungbean and related legumes.     

The Chloroplast Genome Sequence of Mungbean (Vigna radiata) Determined by High-throughput Pyrosequencing: Structural Organization and Phylogenetic Relationships

Mungbean is an economically important crop which is grown principally for its protein-rich dry seeds. However, genomic research of mungbean has lagged behind other species in the Fabaceae family. Here, we reported the complete chloroplast (cp) genome sequence of mungbean obtained by the 454 pyrosequencing technology. The mungbean cp genome is 151 271 bp in length which includes a pair of inverted repeats (IRs) of 26 474 bp separated by a small single-copy region of 17 427 bp and a large single-copy region of 80 896 bp. The genome contains 108 unique genes and 19 of these genes are duplicated in the IR. Of these, 75 are predicted protein-coding genes, 4 ribosomal RNA genes and 29 tRNA genes. Relative to other plant cp genomes, we observed two distinct rearrangements: a 50-kb inversion between accD/rps16 and rbcL/trnK-UUU, and a 78-kb rearrangement between trnH/rpl14 and rps19/rps8. We detected sequence length polymorphism in the cp homopolymeric regions at the intra- and inter-specific levels in the Vigna species. Phylogenetic analysis demonstrated a close relationship between Vigna and Phaseolus in the phaseolinae subtribe and provided a strong support for a monophyletic group of the eurosid I.     

Gibberellic Acid and Sulfur-Mediated Reversal of Cadmium-Inhibited Photosynthetic Performance in Mungbean (Vigna radiata L.) Involves Nitric Oxide

Journal of Plant Growth Regulation - Gibberellic acid (GA) and sulfur (S) have been known to modulate physiological processes of plants in normal and stressful conditions. Cultivars of mungbean...     

Chlorophyll mutations in mungbean (Vigna radiata (L.) Wilczek)

Summary Twenty mutants isolated from Latisail, Jhingasail and Pankaj varieties of rice (Oryza sativa L.) were screened for two aspects of nutritive quality, namely crude protein content and distribution pattern of protein in the endosperm. Observations revealed a wide variation for both characters, and while there was no consistent association between protein content and test grain weight, which varied between varieties, a positive correlation between protein content and grain sterility was noted. In a few mutants protein distribution was observed to be varied and showed a similarity to optimum milling characteristics.     

Isolation and expression of an elongation-dependent gene of mung bean (Vigna radiata) hypocotyl

A cDNA clone of an auxin up-regulated gene, ARG8 , was isolated from hypocotyl sections of etiolated mung bean [ Vigna radiata (L.) Wilczek] seedlings by differential screening. The deduced amino acid sequence suggested that ARG8 may encode a cell wall protein. The steady state mRNA level of ARG8 increased by treatment of hypocotyl sections not only with indole-3-acetic acid (IAA) but also with fusicoccin, and the auxin inducibility was inhibited by the addition of 0.3 M mannitol in the incubation medium. This indicated that it was not auxin but elongation that regulated the expression of ARG8 . The promoter activity of the 5'-flanking region of ARG8 was determined by assaying the transient expression of a luciferase fusion gene that was introduced into mung bean hypocotyl sections by the particle bombardment technique. The basal activity of the ARG8 upstream region was about a few tenths of that of a modified cauliflower mosaic virus 35S promoter, and it was increased a few fold by treatment with IAA. The auxin inducibility was completely suppressed by the addition of mannitol. A 5'-deletion analysis showed that a 53-bp region in the ARG8 promoter was important for the basal and elongation-dependent promoter activities.     

Orthophosphate is a non-essential activator of Vigna radiata flavokinase.

The ATP-dependent phosphorylation of riboflavin to FMN by flavokinase from Vigna radiata was activated by orthophosphate (Pi) in a concentration dependent manner. Pi affected both the K(m) and Vmax, indicating that it is a non-essential, mixed type activator. The extent of activation by Pi was dependent on the cation (Mg2+ or Zn2+). Activation by other anions could be correlated to similarity to Pi in molecular size and structure. These observations suggest the presence of a binding site(s) for a phosphate-like anion on flavokinase.     

Molecular studies on mungbean (Vigna radiata (L.) Wilczek) and ricebean (Vigna umbellata (Thunb.)) interspecific hybridisation for Mungbean yellow mosaic virus resistance and development of species-specific SCAR marker for ricebean

The aim of this study was to identify the molecular markers (SSR, RAPD and SCAR) associated with Mungbean yellow mosaic virus resistance in an interspecific cross between a mungbean variety, VRM (Gg) 1 X a ricebean variety, TNAU RED. The parental survey was carried out by using 118 markers (including 106 azuki bean primers, seven mungbean primers and five ricebean primers). This study revealed that 42 azuki bean markers (39.62%) and four mungbean markers (54.07%) showed parental polymorphism. These polymorphic markers were surveyed among the 187 F₂ plants and the results showed distorted segregation or chromosomal elimination at all the marker loci (thus, deviating from the expected 1:2:1 segregation). None of the plants harboured the homozygous ricebean allele for the markers surveyed and all of them were skewed towards mungbean, VRM (Gg) 1, allele, except a few plants which were found to be heterozygous for few markers. Among the 42 azuki bean SSR markers surveyed, only 10 markers produced heterozygotic pattern in six F₂ lines viz. 3, 121, 122, 123, 185 and 186. These markers were surveyed in the corresponding F₃ individuals, which too skewed towards the mungbean allele. In this study, one species-specific SCAR marker was developed for ricebean by designing primers from the sequenced putatively species-specific RAPD bands. A single, distinct and brightly resolved band of 400?bp was found amplified only in the resistant parent, TNAU RED, and not in any other six species or in the resistant or the susceptible bulks of the mapping population clearly indicated the identification of SCAR marker specific to the ricebean.     

Rhizodeposition of Nitrogen and Carbon by Mungbean (Vigna radiata L.) and Its Contribution to Intercropped Oats (Avena nuda L.)

Compounds released by mungbean roots potentially represent an enormous source of nitrogen (N) and carbon (C) in mungbean-oat intercropping systems. In this study, an in situ experiment was conducted using a ¹⁵N - ¹³C double stem-feeding method to measure N and C derived from the rhizodeposition (NdfR and CdfR) of mungbean and their transfer to oats in an intercropping system. Mungbean plants were sole cropped (S) or intercropped (I) with oat. The plants were labeled 5 weeks after planting and were harvested at the beginning of pod setting (I_p and S_p) and at maturity (I_m and S_m). More than 60% and 50% of the applied ¹⁵N and ¹³C, respectively, were recovered in each treatment, with ¹⁵N and ¹³C being quite uniformly distributed in the different plant parts. NdfR represented 9.8% (S_p), 9.2% (I_p), 20.1% (S_m), and 21.2% (I_m) of total mungbean plant N, whereas CdfR represented 13.3% (S_p), 42.0% (I_p), 15.4% (S_m), and 22.6% (I_m) of total mungbean plant C. When considering the part of rhizodeposition transferred to associated oat, intercropping mungbean released more NdfR and CdfR than mungbean alone. About 53.4–83.2% of below-ground plant N (BGP-N) and 58.4–85.9% of BGP-C originated from NdfR and CdfR, respectively. The N in oats derived from mungbean increased from 7.6% at the pod setting stage to 9.7% at maturity, whereas the C in oats increased from 16.2% to 22.0%, respectively. Only a small percentage of rhizodeposition from mungbean was transferred to oats in the intercropping systems, with a large percentage remaining in the soil. This result indicates that mungbean rhizodeposition might contribute to higher N and C availability in the soil for subsequent crops.     

Isolation and cDNA cloning of an Em-like protein from mung bean (Vigna radiata) axes

Until now no 'early-methionine-labelled' (Em) proteins have been reported in the Fabaceae. To check whether a previously isolated low-molecular mass albumin from dry mung bean embryonic axes possibly corresponded to an Em-like protein, the protein was purified, sequenced and its cDNA clone isolated and characterized. N-terminal sequencing of cyanogen bromide cleavage products of the protein revealed homology with previously described Em-like proteins from other species. Analysis of cDNA clones encoding the mung bean Em protein revealed the presence of two classes of Em proteins and confirmed their homology to the previously characterized Em-like proteins. In vivo labelling and northern blot analysis further demonstrated that the mung bean protein is synthesized during early germination of the axes and that abscisic acid (ABA) extends its synthesis. It appears, therefore, that legumes also contain maturation-specific, ABA-responsive Em-like proteins.     

Purification and characterization of tubulin from mung bean (Vigna radiata)

Tubulin has been purified from mung bean seedling by Zn²⁺-induced polymerization. Both α- and β-subunits of mung bean tubulin are different from those of brain tubulin in electrophoretic mobility, colchicine binding and peptide map. Heterogeneity of mung bean tubulin has also been documented suggesting diversification of tubulin despite its conserved nature in general.