Revision of the <Emphasis Type="Italic">Rhynchospora glomerata</Emphasis> species complex,focusing on the taxonomic status of <Emphasis Type="Italic">R. leptocarpa</Emphasis> (Cyperaceae)

Rhynchospora glomerata and its closest relatives comprise a group of beakesedges widespread and frequent in much of North America. The classification of the R. glomerata complex remains unresolved and controversial. The goals of this study are to determine the number of taxa in the complex and their ranks, and identify their best diagnostic characters. Measurements of eight characters from each of 101 specimens from throughout the geographic range of the complex furnished data for morphometric analyses. These analyses reveal the R. glomerata complex contains three species and no infraspecific taxa: R. capitellata, R. glomerata, and R. leptocarpa. We detected 10 validly published basionyms in the complex, five of which required lectotypification. Accordingly, we designated lectotypes for R. glomerata var. discutiens, R. glomerata var. minor, R. glomerata var. paniculata, and R. glomerata var. robustior, and the second-step lectotype for R. capitellata var. controversa.     

Development of <Emphasis Type="Italic">Brassica oleracea</Emphasis>-<Emphasis Type="Italic">nigra</Emphasis> monosomic alien addition lines: genotypic,cytological and morphological analyses

Key message

We report the development and characterization of Brassica oleracea - nigra monosomic alien addition lines (MAALs) to dissect the Brassica B genome.

Abstract

Brassica nigra (2n = 16, BB) represents the diploid Brassica B genome which carries many useful genes and traits for breeding but received limited studies. To dissect the B genome from B. nigra, the triploid F₁ hybrid (2n = 26, CCB) obtained previously from the cross B. oleracea var. alboglabra (2n = 18, CC) × B. nigra was used as the maternal parent and backcrossed successively to parental B. oleracea. The progenies in BC₁ to BC₃ generations were analyzed by the methods of FISH and SSR markers to screen the monosomic alien addition lines (MAALs) with each of eight different B-genome chromosomes added to C genome (2n = 19, CC + 1B_1?8), and seven different MAALs were established, except for the one with chromosome B2 which existed in one triple addition. Most of these MAALs were distinguishable morphologically from each other, as they expressed the characters from B. nigra differently and at variable extents. The alien chromosome remained unpaired as a univalent in 86.24% pollen mother cells at diakinesis or metaphase I, and formed a trivalent with two C-genome chromosomes in 13.76% cells. Transmission frequency of all the added chromosomes was far higher through the ovules (averagely 14.40%) than the pollen (2.64%). The B1, B4 and B5 chromosomes were transmitted by female at much higher rates (22.38–30.00%) than the other four (B3, B6, B7, B8) (5.04–8.42%). The MAALs should be valuable for exploiting the genome structure and evolution of B. nigra.

     

Genetic composition of interspecific potato somatic hybrids and autofused 4<Emphasis Type="Italic">x</Emphasis> plants evaluated by DArT and cytoplasmic DNA markers

Key message

Using DArT analysis, we demonstrated that all Solanum × michoacanum (+) S. tuberosum somatic hybrids contained all parental chromosomes. However, from 13.9 to 29.6 % of the markers from both parents were lost in the hybrids.

Abstract

Somatic hybrids are an interesting material for research of nucleus-cytoplasm interaction and sources of new nuclear and cytoplasmic combinations. Analyses of genomes of somatic hybrids are essential for studies on genome compatibility between species, its evolution and are important for their efficient exploitation. Diversity array technology (DArT) permits analysis of the composition of nuclear DNA of somatic hybrids. The nuclear genome compositions of 97 Solanum × michoacanum (+) S. tuberosum [mch (+) tbr] somatic hybrids from five fusion combinations and 11 autofused 4x mch were analyzed for the first time based on DArT markers. Out of 5358 DArT markers generated in a single assay, greater than 2000 markers were polymorphic between parents, of which more than 1500 have a known chromosomal location on potato genetic or physical map. DArT markers were distributed along the entire length of 12 chromosomes. We noticed elimination of markers of wild and tbr fusion components. The nuclear genome of individual somatic hybrids was diversified. Mch is a source of resistance to Phytophthora infestans. From 97 mch (+) tbr somatic hybrids, two hybrids and all 11 autofused 4x mch were resistant to P. infestans. The analysis of the structure of particular hybrids’ chromosomes indicated the presence of markers from both parental genomes as well as missing markers spread along the full length of the chromosome. Markers specific to chloroplast DNA and mitochondrial DNA were used for analysis of changes within the organellar genomes of somatic hybrids. Random and non-random segregations of organellar DNA were noted.

     

<Emphasis Type="Italic">PAD4</Emphasis>, <Emphasis Type="Italic">LSD1</Emphasis> and <Emphasis Type="Italic">EDS1</Emphasis> regulate drought tolerance,plant biomass production,and cell wall properties

Key message

Arabidopsis and poplar with modified PAD4, LSD1 and EDS1 genes exhibit successful growth under drought stress. The acclimatory strategies depend on cell division/cell death control and altered cell wall composition.

Abstract

The increase of plant tolerance towards environmental stresses would open much opportunity for successful plant cultivation in these areas that were previously considered as ineligible, e.g. in areas with poor irrigation. In this study, we performed functional analysis of proteins encoded by PHYTOALEXIN DEFICIENT 4 (PAD4), LESION SIMULATING DISEASE 1 (LSD1) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) genes to explain their role in drought tolerance and biomass production in two different species: Arabidopsis thaliana and Populus tremula × tremuloides. Arabidopsis mutants pad4-5, lsd1-1, eds1-1 and transgenic poplar lines PAD4-RNAi, LSD1-RNAi and ESD1-RNAi were examined in terms of different morphological and physiological parameters. Our experiments proved that Arabidopsis PAD4, LSD1 and EDS1 play an important role in survival under drought stress and regulate plant vegetative and generative growth. Biomass production and acclimatory strategies in poplar were also orchestrated via a genetic system of PAD4 and LSD1 which balanced the cell division and cell death processes. Furthermore, improved rate of cell division/cell differentiation and altered physical properties of poplar wood were the outcome of PAD4- and LSD1-dependent changes in cell wall structure and composition. Our results demonstrate that PAD4, LSD1 and EDS1 constitute a molecular hub, which integrates plant responses to water stress, vegetative biomass production and generative development. The applicable goal of our research was to generate transgenic plants with regulatory mechanism that perceives stress signals to optimize plant growth and biomass production in semi-stress field conditions.

     

Fine mapping of a male sterility gene <Emphasis Type="Italic">ms</Emphasis>-<Emphasis Type="Italic">3</Emphasis> in a novel cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) mutant

Key message

The cucumber male sterility gene ms - 3 was fine mapped in a 76 kb region harboring an MMD1 -like gene Csa3M006660 that may be responsible for the male sterile in cucumber.

Abstract

A cucumber (Cucumis sativus L.) male sterile mutant (ms-3) in an advanced-generation inbred line was identified, and genetic analysis revealed that the male sterility trait was controlled by a recessive nuclear gene, ms-3, which was stably inherited. Histological studies suggested that the main cause of the male sterility was defective microsporogenesis, resulting in no tetrad or microspores being formed. Bulked segregant analysis (BSA) and genotyping of an F₂ population of 2553 individuals were employed used to fine map ms-3, which was delimited to a 76 Kb region. In this region, a single non-synonymous SNP was found in the Csa3M006660 gene locus, which was predicted to result in an amino acid change. Quantitative RT-PCR analysis of Csa3M006660 was consistent with the fact that it plays a role in the early development of cucumber pollen. The protein encoded by Csa3M006660 is predicted to be homeodomain (PHD) finger protein, and the high degree of sequence conservation with homologs from a range of plant species further suggested the importance of the ms-3 non-synonymous mutation. The data presented here provide support for Csa3M006660 as the most likely candidate gene for Ms-3.

     

Application of gliadin polymorphism for pedigree analysis in common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) from Northern Kazakhstan

Gliadins, seed storage proteins, are popular markers effectively employed for the analysis of common wheat. Gliadin electrophoretic patterns are genotype-specific, reproducible, not dependent on growing conditions and are suitable for germplasm identification complementary to molecular markers. Gliadins have been identified and used in wheat from various countries, but prior to this study little was known about gliadin polymorphism in wheat from Kazakhstan. In this study, 48 alleles of six gliadin-coding loci were identified in 43 cultivars of spring wheat from Northern Kazakhstan. The alleles Gli-A1 f , Gli-B1 e , Gli-D1 a , Gli-A2 p , Gli-B2 d and Gli-D2 e had maximal frequencies in each of the six loci. Identified Gli alleles in the loci formed ‘Gliadin Genetic Formula’ unique for each studied variety, and these were compared to the published data from previously analyzed wheat varieties. Pedigree analysis of 43 varieties studied for gliadin polymorphisms indicated that some Gli alleles were conserved and inherited from the progenitor cultivar Akmolinka 1. In contrast, other Gli alleles were replaced by those from modern germplasms. It is assumed that a higher frequency of gliadin alleles can be associated with the selection of genotypes with improved traits for yield and seed quality in the studied wheat cultivars from Northern Kazakhstan.     

Four mononuclear platinum(II) complexes: synthesis,DNA/BSA binding,DNA cleavage and cytotoxicity

Four new platinum(II) complexes: Pt^II L1·H₂O (C1, H₂ L1 = C₂₀H₁₆N₂O₂), Pt^II L2Cl₂ (C2, L2 = C₂₂H₁₆N₂O₂), Pt^II L3Cl₂·H₂O (C3, L3 = C₂₀H₁₆N₂), Pt^II L4Cl₂·0.4H₂O (C4, L4 = C₁₈H₁₄N₄) have been synthesized and characterized by using various physico-chemical techniques. The binding interaction of the four platinum(II) complexes C1–C4 with calf thymus (CT)-DNA has been investigated by UV–Vis and fluorescence emission spectrometry. The apparent binding constant (K _app) values follow the order: C3 > C1 > C2 > C4. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the four platinum(II) complexes C1–C4 showed that the quenching mechanism might be a static quenching procedure. For C1–C4, the number of binding sites was about one for BSA and the binding constants follow the order: C3 (7.08 × 10⁵M^?1) > C1 (2.82 × 10⁵M^?1) > C2 (0.85 × 10⁵M^?1) > C4 (0.15 × 10⁵M^?1). With the single condition change such as absence of an external agent, the DNA cleavage abilities of C3 exhibit remarkable changes. In addition, the cytotoxicity of C3 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) were examined by MTT and showed better antitumor effects on the tested cells.     

Combined drought and heat stress in <Emphasis Type="Italic">Camellia oleifera</Emphasis> cultivars: leaf characteristics,soluble sugar and protein contents,and Rubisco gene expression

Key message

Leaf relative water content, leaf area, leaf fresh weight, and SPAD chlorophyll meter readings along with Co - rbcL and Co - rbcS expression can be used for evaluating Camellia oleifera responses to combined drought and heat stress and subsequent recovery after rainfall events.

Abstract

Leaf characteristics, soluble protein and total soluble sugar contents as well as Rubisco-related gene expression in three cultivars of C. oleifera were measured during a combined drought and heat stress period and after subsequent rainfall events. Leaf relative water content (RWC) was significantly correlated with leaf area (LA), leaf fresh weight (FW), SPAD chlorophyll meter readings, and the levels of Co-rbcL and Co-rbcS expression. Results suggest that leaf RWC, LA, leaf FW, SPAD readings together with Co-rbcL and Co-rbcS expression can be used for evaluating responses of C. oleifera cultivars to combined drought and heat stress and subsequent recovery after rainfall events. Rubisco activase might be used for evaluating plant recovery after rainfall. This study identified cultivars differing in tolerance to the combined stress and recovery. Information derived from this study should be valuable for improving survivability and productivity of C. oleifera cultivars.

     

Complete chloroplast genome sequences of <Emphasis Type="Italic">Solanum commersonii</Emphasis> and its application to chloroplast genotype in somatic hybrids with <Emphasis Type="Italic">Solanum tuberosum</Emphasis>

Key message

Chloroplast genome of Solanum commersonii and S olanum tuberosum were completely sequenced, and Indel markers were successfully applied to distinguish chlorotypes demonstrating the chloroplast genome was randomly distributed during protoplast fusion.

Abstract

Somatic hybridization has been widely employed for the introgression of resistance to several diseases from wild Solanum species to overcome sexual barriers in potato breeding. Solanum commersonii is a major resource used as a parent line in somatic hybridization to improve bacterial wilt resistance in interspecies transfer to cultivated potato (S. tuberosum). Here, we sequenced the complete chloroplast genomes of Lz3.2 (S. commersonii) and S. tuberosum (PT56), which were used to develop fusion products, then compared them with those of five members of the Solanaceae family, S. tuberosum, Capsicum annum, S. lycopersicum, S. bulbocastanum and S. nigrum and Coffea arabica as an out-group. We then developed Indel markers for application in chloroplast genotyping. The complete chloroplast genome of Lz3.2 is composed of 155,525 bp, which is larger than the PT56 genome with 155,296 bp. Gene content, order and orientation of the S. commersonii chloroplast genome were highly conserved with those of other Solanaceae species, and the phylogenetic tree revealed that S. commersonii is located within the same node of S. tuberosum. However, sequence alignment revealed nine Indels between S. commersonii and S. tuberosum in their chloroplast genomes, allowing two Indel markers to be developed. The markers could distinguish the two species and were successfully applied to chloroplast genotyping (chlorotype) in somatic hybrids and their progenies. The results obtained in this study confirmed the random distribution of the chloroplast genome during protoplast fusion and its maternal inheritance and can be applied to select proper plastid genotypes in potato breeding program.

     

The seed dormancy allele <Emphasis Type="Italic">TaSdr</Emphasis>-<Emphasis Type="Italic">A1a</Emphasis> associated with pre-harvest sprouting tolerance is mainly present in Chinese wheat landraces

Key message

We cloned TaSdr - A1 gene, and developed a gene-specific marker for TaSdr - A1 . A QTL for germination index at the TaSdr - A1 locus was identified in the Yangxiaomai/Zhongyou 9507 RIL population.

Abstract

Pre-harvest sprouting (PHS) affects yield and end-use quality in bread wheat (Triticum aestivum L.). In the present study we found an association between the TaSdr-A1 gene and PHS tolerance in bread wheat. TaSdr-A1 on chromosome 2A was cloned using a homologous cloning approach. Sequence analysis of TaSdr-A1 revealed an SNP at position 643, with the G allele being present in genotypes with lower germination index (GI) values and A in those with higher GI. These alleles were designated as TaSdr-A1a and TaSdr-A1b, respectively. A cleaved amplified polymorphism sequence (CAPS) marker Sdr2A based on the SNP was developed, and linkage mapping and QTL analysis were conducted to confirm the association between TaSdr-A1 and seed dormancy. Sdr2A was located in a 2.9 cM interval between SSR markers Xgwm95 and Xgwm372. A QTL for GI at the TaSdr-A1 locus explained 6.6, 7.3, and 8.2 % of the phenotypic variances in a Yangxiaomai/Zhongyou 9507 RIL population grown at Beijing, Shijiazhuang, and the averaged data from the two environments, respectively. Two sets of Chinese wheat cultivars used for validating the TaSdr-A1 polymorphism and the corresponding gene-specific marker Sdr2A showed that TaSdr-A1 was significantly associated with GI. Among 29 accessions with TaSdr-A1a, 24 (82.8 %) were landraces, indicating the importance of Chinese wheat landraces as sources of PHS tolerance. This study identified a novel PHS resistance allele TaSdr-A1a mainly presented in Chinese landraces and it is likely to be the causal gene for QPhs.ccsu-2A.3, providing new information for an understanding of seed dormancy.

     

Update on <Emphasis Type="Italic">transparent testa</Emphasis> mutants from <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>: characterisation of new alleles from an isogenic collection

Main conclusion

We present a comprehensive overview on flavonoid-related phenotypes of A. thaliana tt and tds mutants, provide tools for their characterisation, increase the number of available alleles and demonstrate that tds3 is allelic to tt12 and tds5 to aha10.Flavonoid biosynthesis is one of the best-studied secondary metabolite pathways in plants. In the model system Arabidopsis thaliana it leads to the synthesis of three phenolic compound classes: flavonol glycosides, anthocyanins and proanthocyanidins (PAs). PAs appear brown in their oxidised polymeric forms, and most A. thaliana mutants impaired in flavonoid accumulation were identified through screens for lack of this seed coat pigmentation. These mutants are referred to as transparent testa (tt) or tannin-deficient seed (tds). More than 20 mutants of these types have been published, probably representing most of the genes relevant for PA accumulation in A. thaliana. However, data about the genes involved in PA deposition or oxidation are still rather scarce. Also, for some of the known mutants it is unclear if they represent additional loci or if they are allelic to known genes. For the present study, we have performed a systematic phenotypic characterisation of almost all available tt and tds mutants and built a collection of mutants in the genetic background of the accession Columbia to minimise effects arising from ecotype variation. We have identified a novel tt6 allele from a forward genetic screen and demonstrated that tds3 is allelic to tt12 and tds5 to aha10.

     

Round fruit shape in WI7239 cucumber is controlled by two interacting quantitative trait loci with one putatively encoding a tomato <Emphasis Type="Italic">SUN</Emphasis> homolog

Key message

QTL analysis revealed two interacting loci, FS1.2 and FS2.1, underlying round fruit shape in WI7239 cucumber; CsSUN , a homolog of tomato fruit shape gene SUN , was a candidate for FS1.2.

Abstract

Fruit size is an important quality and yield trait in cucumber, but its genetic basis remains poorly understood. Here we reported QTL mapping results on fruit size with segregating populations derived from the cross between WI7238 (long fruit) and WI7239 (round fruit) inbred cucumber lines. Phenotypic data of fruit length and diameter were collected at anthesis, immature and mature fruit stages in four environments. Ten major-effect QTL were detected for six traits; synthesis of information from these QTL supported two genes, FS1.2 and FS2.1, underlying fruit size variation in the examined populations. Under the two-gene model, deviation from expected segregation ratio in fruit length and diameter among segregating populations was observed, which could be explained mainly by the interactions between FS1.2 and FS2.1, and segregation distortion in the FS2.1 region. Genome-wide candidate gene search identified CsSUN, a homolog of the tomato fruit shape gene SUN, as the candidate for FS1.2. The round-fruited WI7239 had a 161-bp deletion in the first exon of CsSUN, and its expression in WI7239 was significantly lower than that in WI7238. A marker derived from this deletion was mapped at the peak location of FS1.2 in QTL analysis. Comparative analysis suggested the melon gene CmSUN-14, a homolog of CsSUN as a candidate of the fl2/fd2/fw2 QTL in melon. This study revealed the unique genetic architecture of round fruit shape in WI7239 cucumber. It also highlights the power of QTL analysis for traits with a simple genetic basis but their expression is complicated by other factors.

     

<Emphasis Type="Italic">ZmCCD7/ZpCCD7</Emphasis> encodes a carotenoid cleavage dioxygenase mediating shoot branching

Main conclusion

ZmCCD7/ZpCCD7 encodes a carotenoid cleavage dioxygenase that may mediate strigolactone biosynthesis highly responsive to phosphorus deficiency and undergoes negative selection over domestication from Zea ssp. parviglumis to Zea mays.Carotenoid cleavage dioxygenase 7 (CCD7) functions to suppress shoot branching by controlling strigolactone biosynthesis. However, little is known about CCD7 and its functions in maize and its ancestor (Zea ssp. parviglumis) with numerous shoot branches. We found that ZmCCD7 and ZpCCD7 had the same coding sequence, indicating negative selection of the CCD7 gene over domestication from Zea ssp. parviglumis to Zea mays. CCD7 expression was highly responsive to phosphorus deficiency in both species, especially in the meristematic zone and the pericycle of the elongation zone of maize roots. Notably, the crown root had the strongest ZmCCD7 expression in the meristematic zone under phosphorus limitation. Transient expression of GFP tagged ZmCCD7/ZpCCD7 in maize protoplasts indicated their localization in the plastid. Further, ZmCCD7/ZpCCD7 efficiently catalyzed metabolism of six different linear and cyclic carotenoids in E. coli, and generated β-ionone by cleaving β-carotene at the 9,10 (9′,10′) position. Together with suppression of shoot branching in the max3 mutant by transformation of ZmCCD7/ZpCCD7, our work suggested that ZmCCD7/ZpCCD7 encodes a carotenoid cleavage dioxygenase mediating strigolactone biosynthesis in maize and its ancestor.