Genetic study of a new color of the beet Beta vulgaris L.

A new genetic character of the beet Beta vulgaris L., named stem color, was described and studied genetically. This character was shown to be dominant and monogenically inherited. The first-year beet plants with the genotype Stc/_ have red leafstalks, weakly colored central rib, and colored storage root; however, the root itself is not colored. The second-year plants have a red-colored low third of the floral shoot. The plants with the genotype stc/stc are uncolored. The Stc gene was localized to the first linkage group at a distance of 17.5 ± 2.1% crossing over units from the gene B (Bolting), which controls the annual-perennial habit of beet.     

Molecular cloning of stanniocalcin 1 and its extracorpuscular regulation by salinity and Ca2+ in the Japanese flounder

Stanniocalcin 1 (Stc1) was originally identified as an anti-hypercalcemic hormone produced by the corpuscles of Stannius (CS) associated with the kidney in teleosts. While the stc1 gene is expressed in various tissues in fishes, its role and regulation in extra-CS tissues are unexplored. In the present study, we characterized a cDNA of stc1 in a euryhaline fish, the Japanese flounder (Paralichyhus olivaceus), and examined its expression in peripheral tissues in response to different salinities and Ca2+ ion concentrations. The Japanese flounder stc1 cDNA (1331 bp) encodes a preprohormone of 251 amino acids (aa), with a signal peptide of 17 aa and a pro-sequence peptide of 15 aa followed by the mature protein of 219 aa. The deduced aa sequence of Japanese flounder stc1 showed highest sequence identity (94.0%) with the European flounder Stc1 among fish and mammalian species, but lower identity to zebrafish, pufferfish, and human STC2 (23.1-25.4%). Lowered environmental salinity resulted in a decrease in stc1 mRNA expression in vivo in the gills, kidney, intestine, and CS glands of the Japanese flounder. Furthermore, we found that extracellular Ca2+ increased steady-state stc1 mRNA levels in gill and kidney cells as well as in the CS cells. Our findings suggest that Stc1 synthesis in the ionregulatory tissues is responsive to environmental salinity and Ca2+ level.     

Characterization of the monoterpene synthase gene tps26, the ortholog of a gene induced by insect herbivory in maize

Plants damaged by insects can synthesize and release volatile chemicals that attract natural enemies of the herbivore. The maize (Zea mays subsp. mays) terpene synthase gene stc1 is part of that indirect defense response, being induced in seedling blades in response to herbivory by beet army worm. Many genes in maize are duplicated because of a past whole-genome duplication event, and several of these orthologs display different expression patterns. We report here the isolation and characterization of tps26 and confirm by homology and synteny criteria that it is the ortholog of stc1. Prior genetic analysis revealed that the stc1 function is not duplicated, raising the interesting question of how the two orthologs have become differentiated in their expression. tps26 encodes a 633-amino acid protein that is highly conserved with STC1. Like stc1, tps26 is induced by wounding, but in the roots and leaf sheath, instead of the blade, and not in response to beet army worm feeding. tps26 maps near a quantitative trait locus for Southwestern corn borer resistance, making it a plausible candidate gene for that quantitative trait locus. However, while possessing highly polymorphic tps26 alleles, the resistant and susceptible parents of the mapping population do not differ in levels of tps26 expression. Moreover, tps26 is not induced specifically by Southwestern corn borer feeding. Therefore, although they share a wounding response, the stc1 and tps26 maize orthologs differ in their tissue specificity and their induction by insect herbivores. The N termini of STC1 and TPS26 are predicted to encode plastid transit peptides; fusion proteins of green fluorescent protein to either N terminus localized to the plastid, confirming that prediction. The mature proteins, but not the respective complete proteins, were active and synthesized a blend of monoterpenes, indicating that they are monoterpene synthases. A gene closely related to stc1/tps26 is found in the sorghum (Sorghum spp.) genome at a location that is not orthologous with stc1. The possible origin of stc1-like genes is discussed.     

超表达AVP1基因提高甜菜的耐低磷和耐盐抗旱性

为探讨H⁺-焦磷酸酶编码基因对甜菜磷吸收和抗性的影响,实现优良基因在甜菜基因工程中的利用,研究在甜菜中超表达拟南芥液泡膜H⁺-焦磷酸酶编码基因AVP1,对转基因甜菜分析其耐低磷、耐盐性和抗旱性。结果显示,AVP1基因在甜菜植株的叶片和块根中表达,且在逆境胁迫下增强表达量响应胁迫;低磷处理条件下,转基因甜菜与野生型甜菜相比具有更高的含磷量,可提高甜菜对磷的吸收利用效率;干旱、盐胁迫处理条件下,AVP1基因在转基因甜菜中显著上升,在盐胁迫或干旱处理条件下,转基因植株的生长受抑程度相对较轻。随着盐和干旱胁迫的加剧,转基因植株体内MDA含量与野生型植株相比较低而脯氨酸含量显著增加,AVP1基因可通过减轻逆境对甜菜细胞膜的损伤及提高甜菜细胞的渗透调节能力,进而增强甜菜对高盐和干旱胁迫的抗性。     

Responses of sugar beet (Beta vulgaris L.) to drought and nutrient deficiency stress

The responses of two sugar beet genotypes, 24367 (putative droughttolerant) and N6 (putative drought intolerant), to drought and nutrientdeficiency stress were investigated in an attempt to identify reliable andsensitive indicators of stress tolerance. In glasshouse-grown plants of bothgenotypes, relative water content (RWC) of the leaves decreased and leaftemperature increased in response to drought stress. Genotype differences inresponse to drought included leaf RWC, glycine betaine accumulation, alterationof shoot/root ratio and production of fibrous roots. Thus, in comparison to N6,genotype 24367 lost less water from leaves, produced more fibrous roots,produced more glycine betaine in shoots and tap roots and had a much reducedshoot/root ratio in response to withholding water for up to 215 h.The hydraulic conductance and sap flow of sugar beet seedlings grown innutrientculture decreased when subjected to nitrogen deficiency stress. Under nitrogensufficient conditions sap flow was greater in 24367 than in N6. The resultsindicate that genotype 24367 is more tolerant to stresses induced by water andnitrogen deficiency and that increased fibrous root development may be a majorfactor in increasing sap flow via a concomitant enhancement of aquaporinactivity.     

Using coloured roots to study root interaction and competition in intercropped legumes and non-legumes

Aims Root interactions between neighbour plants represent a fundamental aspect of the competitive dynamics in pure stand and mixed cropping systems. The comprehension of such phenomena places big methodological challenges, and still needs clarification. The objectives of this work were (i) to test if a species with coloured roots can be used to examine the interaction in a legume-non-legume intercropping system; (ii) to verify the importance of initial root growth on the successive root development of mixture component plants; (iii) to test if the root interaction in the shallow layers has consequences for deep root growth and (iv) to compare the effect of intraspecific and interspecific competition on root development and biomass growth.Methods A detailed study on root growth and interaction was carried out using rhizotron tubes where two legume species were grown in pure stands or were intercropped with red beet, a variety of Beta vulgaris L. with clear red roots. Within the rhizotrons, the three species were grown either without competitors, with two plants of the same species to measure intraspecific competition or with one legume and one red beet plant to study interspecific competition. The use of mixtures where one component has clearly coloured roots, together with several scalar measurements of root depth and proliferation, allowed the measurement of the root system of each species when grown in the mixtures.Important findings The use of rhizotron tubes coupled with species with coloured roots represented a valuable method to study the belowground interaction in mixed cropping systems. The initial root growth was a very important feature for the subsequent dominance of a species and it was not related to seed dimension. Initial root growth was also important because the root interactions in the shallower soil layers were found to influence the root growth in deeper soil. The root system of the red beet showed much faster and deeper growth than that of the legumes, and made red beet the dominant component in the mixtures while the legume root system was confined to the shallower soil layer. Intraspecific competition was well tolerated by the legumes, but it was limiting for the highly competitive red beet. The outcome of root interaction between neighbour plants was confirmed to be species-specific as it changed according to the intensity of the competitive effect/response of each species of the mixture: both legumes were slightly affected by the intraspecific and highly affected by interspecific competition while red beet was more affected by intraspecific competition but strongly dominant when intercropped with legumes.     

Epigenetic variation of the choriflowered-symflowered character in the symflowered sugar beet line SOAN-14

The effect of 5-azacytidine on the variation of the choriflowered (CF)-symflowered (SF) character in sugar beet was studied in several generations obtained via seed reproduction. The epimutagen (5-azacytidine) significantly reduced the number of flowers in glomerate inflorescences in the year of seed treatment and in the next generation (Az₁), leading to the appearance of plants with single flowers in bract axils of a flower stalk. The CF character resulting from epimutagene treatment of sugar beet seeds (plants with genotype M ^Z M ^Z ) was inherited as a monohybrid character in both zygotic and apozygotic seed progenies. The proportion of the CF and SF phenotypes in the progenies was affected by the chromatid number in the chromosomes (mixoploidy of the cell populations). Alleles of the Mm locus were found to affect the variation in phytomere organization of flower stalks.     

Identification of the predominant nonrestoring allele for Owen-type cytoplasmic male sterility in sugar beet (Beta vulgaris L.): development of molecular markers for the maintainer genotype

Hybrid seed production in sugar beet relies on cytoplasmic male sterility (CMS). As time-consuming and laborious test crosses with a CMS tester are necessary to identify maintainer lines, development of a marker-assisted selection method for the rf gene (the nonrestoring allele of restorer-of-fertility locus) is highly desirable for sugar-beet breeding. To develop such a method, we investigated genetic variation at the Rf1 locus, one of two Rf loci known in sugar beet. After HindIII-digestion, genomic DNAs from beet plants known to have a restoring Rf1 allele yielded a range of hybridization patterns on agarose gels, indicating that Rf1 is a multi-allelic locus. However, the hybridization patterns of 22 of 23 maintainer lines were indistinguishable. The nucleotide sequences of the rf1 coding regions of these 22 maintainer lines were found to be identical, confirming that the lines had the same rf1 allele. Two PCR markers were developed that targeted a downstream intergenic sequence and an intron of Rf1. The electrophoretic patterns of both markers indicated multiple Rf1 alleles, one of which, named the dd(L) type, was associated with the maintainer genotype. To test the validity of marker-assisted selection, 147 sugar beet plants were genotyped using these markers. Additionally, the 147 sugar beet plants were crossed with CMS plants to determine whether they possessed the maintainer genotype. Analysis of 5038 F1 offspring showed that 53 % of the dd(L) plants, but none of the plants with other alleles, had the maintainer genotype. Thus, selection for the dd(L) type considerably enriched the proportion of plants with the maintainer genotype.     

Nuclear magnetic resonance: a tool for imaging belowground damage caused by Heterodera schachtii and Rhizoctonia solani on sugar beet

Belowground symptoms of sugar beet caused by the beet cyst nematode (BCN) Heterodera schachtii include the development of compensatory secondary roots and beet deformity, which, thus far, could only be assessed by destructively removing the entire root systems from the soil. Similarly, the symptoms of Rhizoctonia crown and root rot (RCRR) caused by infections of the soil-borne basidiomycete Rhizoctonia solani require the same invasive approach for identification. Here nuclear magnetic resonance imaging (MRI) was used for the non-invasive detection of belowground symptoms caused by BCN and/or RCRR on sugar beet. Excessive lateral root development and beet deformation of plants infected by BCN was obvious 28 days after inoculation (dai) on MRI images when compared with non-infected plants. Three-dimensional images recorded at 56 dai showed BCN cysts attached to the roots in the soil. RCRR was visualized by a lower intensity of the MRI signal at sites where rotting occurred. The disease complex of both organisms together resulted in RCRR development at the site of nematode penetration. Damage analysis of sugar beet plants inoculated with both pathogens indicated a synergistic relationship, which may result from direct and indirect interactions. Nuclear MRI of plants may provide valuable, new insight into the development of pathogens infecting plants below- and aboveground because of its non-destructive nature and the sufficiently high spatial resolution of the method.     

Backcrossing of nematode-resistant sugar beet: a second nematode resistance gene at the locus containing Hs1pro-1?

Beet cyst nematode-resistant sugar beet plants, containing the Hs1^pro-1 locus from Beta procumbens, show a female transmission frequency of the resistance of ca. 90%. Such plants often suffer from tumour formation on leaves and root systems, and from the occurrence of a so-called multi-top phenotype. With the aim of obtaining resistant sugar beet material lacking these negative traits, nematode-resistant plants with a reduced size of the chromosome segment of the wild beet that carries the Hs1^pro-1 gene were selected from backcrosses between the resistant stocks B883 or AN1-65-2 and susceptible sugar beet (Beta vulgaris). Analysis of such plants, referred to as Sat-minus plants, showed that the transmission frequency of the resistance to subsequent generations had dropped dramatically to ca. 0.5%. The multi-top phenotype was still present in the newly selected material, indicating that improvement of the resistant sugar beet material by further backcrossing will be hard to achieve. Two of the selected resistant offspring plants were analysed at the molecular level. With the aid of AFLP markers it was found that the size of the alien chromosome segment had decreased to 35% and 17% of the original size, respectively. Surprisingly, both plants had lost the Hs1^pro-1 nematode resistance gene that recently was isolated from the original introgression material. This shows that more than one gene conferring resistance must be present in the locus in B883 and AN1-65-2 carrying the resistance gene Hs1^pro-1.     

Taproot promoters cause tissue specific gene expression within the storage root of sugar beet

The storage root (taproot) of sugar beet (Beta vulgaris L.) originates from hypocotyl and primary root and contains many different tissues such as central xylem, primary and secondary cambium, secondary xylem and phloem, and parenchyma. It was the aim of this work to characterize the promoters of three taproot-expressed genes with respect to their tissue specificity. To investigate this, promoters for the genes Tlp, His1-r, and Mll were cloned from sugar beet, linked to reporter genes and transformed into sugar beet and tobacco. Reporter gene expression analysis in transgenic sugar beet plants revealed that all three promoters are active in the storage root. Expression in storage root tissues is either restricted to the vascular zone (Tlp, His1-r) or is observed in the whole organ (Mll). The Mll gene is highly organ specific throughout different developmental stages of the sugar beet. In tobacco, the Tlp and Mll promoters drive reporter gene expression preferentially in hypocotyl and roots. The properties of the Mll promoter may be advantageous for the modification of sucrose metabolism in storage roots.     

The Role of Gibberellins in Early Growth and Development of Sugar Beet

Two gibberellin(GA)-like compounds were found in both rootsand shoots of sugar beet plants using the barley endosperm bioassay.One had chromatographic properties similar to GA₃ and GA₁; theother was highly non-polar, relatively inactive in the endospermassay, and may be a new gibberellin. Presence of the GA_3/1-likecompound was confirmed with the dwarf rice bio-assay. The quantityof this GA was relatively high in the root compared with theshoot at the 3–4 leaf stage when the first supernumerarycambia are being formed in the root. As plants developed throughthe 8–9 leaf stage and the 15–16 leaf stage thequantity of GA per unit fresh weight of material decreased. Application of gibberellic acid (GA₃) to the roots of youngsugar beet plants caused a significant increase in root dryweight shortly after treatment and the rate at which supernumerarycambia were produced was increased. Application of GA₃ to asingle petiole caused a significant increase in both root andshoot dry weight. GA₃ applied to either root or shoot causeda reduction in the rate of leaf formation although total leafarea per plant and shoot dry weight were unaffected. The probablerole of GA-like substances in controlling the growth and developmentof young sugar beet plants is discussed.     

黄土高原甜菜叶片生长特性及其对块根产量、含糖量的影响

通过对旱地甜菜叶片生长特性及摘除不同叶组对块根产量,含糖量,显微结构的影响研究,结果表明：甜菜第10-20片叶的叶龄最长,积温最高,是甜菜的主要功能叶;甜菜从第20片叶期起进入块根,糖份增长期,从第55叶期起进入糖份积累期;摘除不同叶组的叶片对甜菜块根产量,含糖量及显微结构均有不同程度降低作用,摘除前期叶组对甜菜块根产量,产糖量,根径减幅较大,摘除后期叶组对块根含糖量,维管束环数,维管束环密度减幅较大;摘除第1-30片叶对甜菜影响最大。     

Systemic inhibition of arbuscular mycorrhiza development by root exudates of cucumber plants colonized by<Emphasis Type="Italic"> Glomus mosseae</Emphasis>

The arbuscular mycorrhizal (AM) non-host plants mustard, sugar beet, lupin and the AM host plant cucumber were used as test plants. Cucumber plants were grown either in the absence of the AM fungus (AMF) Glomus mosseae or in a split-root system, with one side mycorrhizal and one side non-mycorrhizal. Root exudates of the AM non-host plants, the non-mycorrhizal cucumber plants and the mycorrhizal and the non-mycorrhizal side of the split-root system of mycorrhizal cucumber plants were collected and applied to cucumber plants inoculated with the AMF. Root exudates of non-mycorrhizal cucumber plants showed a significant stimulatory effect on root colonization, whereas root exudates from the mycorrhizal and the non-mycorrhizal sides of a split-root system of a mycorrhizal cucumber plant did not show this stimulatory effect and were even slightly inhibitory. Root exudates of the two AM non-host plants mustard and sugar beet significantly reduced root colonization in cucumber plants, whereas no such effect was observed when root exudates of the AM non-host plant lupin were applied.     

Analysis of gene inheritance and expression in hybrids between transgenic sugar beet and wild beets

Reciprocal gene exchange between cultivated sugar beet and wild beets in seed production areas is probably the reason for the occurence of weed beets in sugar beet production fields. Therefore, when releasing transgenic sugar beet plants into the environment, gene transfer to wild beets ( Beta vulgaris ssp. maritima ) has to be considered. In this study the transfer of BNYVV- (beet necrotic yellow vein virus) resistance and herbicide-tolerance genes from two transgenic sugar beet lines that were released in field experiments in 1993 and 1994 in Germany to different wild beet accessions was investigated. In order to evaluate the consequences of outcrossing, manual pollinations of emasculated wild beet plants with homozygous transgenic sugar beet plants were performed. In the resulting hybrids the transgenes were stably inherited according to Mendelian law. Gene expression in leaves and roots of the hybrids was in the same range as in the original transgenic sugar beet plants. Moreover, it was found that in one of the wild beet accessions, transfer and expression of the BNYVV resistance gene did considerably increase the level of virus resistance.     

Polymorphism of PCR profiles and expression of alleles at the locus Adh1 in agamospermous progeny of beet root Beta vulgaris L

A modification of the ISSR amplification method based on using a combination of microsatellite and specific unique primer is proposed and tested. This modification simplifies the detected PCR profiles and allows the examination of DNA regions containing definite genes. Combinations of microsatellite primer Mic2 (5'-gacag-acaga-cagac-a-3') and one of the primers specific to the Adh1 locus, which controls alcohol dehydrogenase (ADH1) in sugar beet, were employed in this work. The microsatellite primer was used in combination with the following specific primers: Adh1f (5'-agagt-gttgg-agagg-gtgtg-ac-3') containing the binding site at the fourth exon of gene Adh1, or Adh1r (5'-act(ct)a-cagca-ag(ct)cc-(ct)ac(ct)g-ctcc-3') that binds to the fifth exon of the same gene. In the agamospermous progeny of individual heterozygous diploid plants of sugar beet with the Adh1-F/Adh1-S genotype, polymorphism of PCR profiles obtained in plants of each of three phenotypic classes (FF, FS, and SS) was detected. Among plants of the progeny from an individual plant that represents the heterozygous phenotypic class FS, differences were revealed not only between the PCR profiles but also in the relative activity of allele isozymes of ADH1.