CLE Peptides in Vascular Development

[ Guodong Wang (Corresponding author)] The plant vascular system consists of two conductive tissues, phloem and xylem. The vascular meristem, namely the (pro‐)cambium, is a stem‐cell tissue that gives rise to both xylem and phloem. Recent studies have revealed that CLAVATA3/Embryo Surrounding Region‐related (CLE) peptides function in establishing the vascular system through interaction with phytohormones. In particular, TDIF/CLE41/CLE44, phloem‐derived CLE peptides, promote the proliferation of vascular cambium cells and prevent them from differentiating into xylem by regulating WOX4 expression through the TDR/PXY receptor. In this review article, we outline recent advances on how CLE peptides function in vascular development in concert with phytohormones through mediating cell‐cell communication. The perspective of CLE peptide signaling in vascular development is also discussed.     

Lactic acid bacteria population dynamics during spontaneous fermentation of radish (<Emphasis Type="Italic">Raphanus sativus</Emphasis> L.) roots in brine

The aim of the present study was to assess the microecosystem development and the dynamics of the lactic acid bacteria population during spontaneous fermentation of radish (Raphanus sativus L.) roots in brine at 20 and 30?°C. In both temperatures, lactic acid bacteria prevailed the fermentation; as a result, the pH value was reduced to ca. 3.6 and total titrable acidity increased to ca. 0.4% lactic acid. Enterococci population increased and formed a secondary microbiota while pseudomonads, Enterobacteriaceae and yeasts/molds populations were below enumeration limit already before the middle of fermentation. Pediococcus pentosaceus dominated during the first days, followed by Lactobacillus plantarum that prevailed the fermentation until the end. Lactobacillus brevis was also detected during the final days of fermentation. A succession at sub-species level was revealed by the combination of RAPD-PCR and rep-PCR analyses. Glucose and fructose were the main carbohydrates detected in brine and were metabolized into lactic acid, acetic acid and ethanol.     

Effect of cytokinins on expression of radish CLE genes

CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION) peptides are peptide phytohormones playing the important role in the regulation of various type meristem development and also in the interaction between plants and parasites and symbionts. At the same time, the interaction of CLE peptides with other phytohormones, participating in these processes, is essentially unstudied. Using real-time RT-PCR, we analyzed expression of some genes encoding CLE peptides in radish (Raphanus sativus var. radicula Pers.) under normal conditions and after treatment with the cytokinin 6-benzyladenine. Even after short-term (30 min) action of cytokinin, expression of group A CLE genes was manifold suppressed, whereas cytokinin did not affect expression of group B CLE genes. Radish lines contrasting in the trait “spontaneous tumor formation” demonstrated similar dynamics of CLE gene expression in response to cytokinin treatment but differed in the levels of their expression. A possibility of interaction between CLE peptides and cytokinins in the spontaneous development of tumors in radish lines is discussed. The important part of the work was the selection of optimal reference genes for the analysis of radish gene expression by real-time RT-PCR method. Most stable expression was observed for the genes of ubiquitin (RsUBQ) and glyceraldehydes-3-phosphate dehydrogenase (RsGAPDH).     

Traits of stem anatomy of some herbaceous members of the family Polygonaceae Juss.

The stem anatomy of the vine Fallopia convolvulus (L.) Á. Löve and that of the self-supporting plant Polygonum patulum M. Bieb. is described. Two groups of tracheary system—few wide elements and many narrow ones—are present in the xylem of the herbaceous vine. The maximum vessel diameters are far greater in Fallopia convolvulus than in Polygonum patulum. Such traits are typical of woody lianas and their self-supporting relatives. The cambium can give rise to wide vessels inward of separate phloem strands in Fallopia convolvulus. The newly formed vessels may substitute for the injured ones. This favors xylem recovery from a drought-induced embolism.     

In search of secondary plants to enhance the efficiency of cabbage seed weevil management

The infestation rate and parasitoid communities of Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) were assessed on seven spring sown brassicaceous plant species to find potential secondary plants that might help increase the parasitism rates of this serious oilseed pest. Over the three-year study, the average infestation rate of pods by C. obstrictus remained below 10 % for each plant species. Despite the low pest abundance, C. obstrictus was parasitized by hymenopteran parasitoids on all plant species, except on Eruca vesicaria subsp. sativa ((Mill.) Thell.). Parasitism rates were remarkably high: between 33.7 and 70.8 % on average and peaked at 94.7 % on Raphanus sativus (L.) var. oleiformis (Pers.). Not only was the parasitism rate high on R. sativus, but it also had a different parasitoid species composition consisting mainly of egg parasitoids (Mymaridae), while on the other plant species larval parasitoids (Pteromalidae) dominated. These findings are important for planning new sustainable pest management approaches.     

Root Structure Indicates the Ability of <Emphasis Type="Italic">Heracleum sosnowskyi</Emphasis> To Absorb Resources Quickly under Optimum Soil Conditions

The structure of the root systems and roots of the invasive plant Heracleum sosnowskyi and the local species H. sibiricum have been compared in three habitats of the southern taiga subzone by the standard methods of plant morphology and anatomy. Differences in the structure of the root systems and roots of H. sosnowskyi and H. sibiricum ensuring the ability of the invasive species to absorb resources under optimum soil conditions have been revealed. These are the occurrence frequency of ephemeral roots, the number of orders of root branching, the size of absorbing roots, and the development of xylem elements.     

<Emphasis Type="Italic">Artemisia arborescens</Emphasis> L. leaf litter: phytotoxic activity and phytochemical characterization

Artemisia arborescens L. is a perennial fast-growing Mediterranean shrub, which releases abundant leaf litter upon soil surface throughout the year. The paper aimed to both evaluate the phytotoxic potential and identify major compounds occurring in the plant leaf litter. Following methanolic maceration of the leaf litter, the crude extract was then sequentially extracted with hexane, chloroform and ethyl acetate through a bio-guided fractionation method. The phytotoxic potential of the methanolic extract and its solvent fractions was assessed in vitro on germination and root growth of two sensitive (Lactuca sativa L., Raphanus sativus L.) and native (Amaranthus retroflexus L., Cynodon dactylon (L.) Pers.) species. Moreover, the most active fractions were chemically characterized by GC–MS and HPTLC analysis. In all species, the physiological processes were highly inhibited by both the methanolic extract and its solvent fractions. Several classes of biologically active phytochemicals such as terpenoids, fatty acids, lignans and phenolic compounds were identified in all fractions. Artemisia arborescens leaf litter could be considered an important source of biologically active phytochemicals, which may have a significant allelopathic impact towards neighbouring species once released into the environment.     

Xylem anatomy and calculated hydraulic conductance of four <Emphasis Type="Italic">Nothofagus</Emphasis> species with contrasting distribution in South-Central Chile

Nothofagus obliqua, N. dombeyi, N. alpina and N. antarctica are characteristic tree species of the temperate forests on the western slopes of the Andes with centres of distribution that differ in their temperature and moisture regimes. We tested branch wood from co-occurring specimens of these species for the inherent differences in xylem anatomy and theoretical hydraulic conductance to evaluate their resistance to drought or frost. The hydraulic conductivity of the xylem was calculated using a modified Hagen–Poiseuille equation and related to wood density. Conduit dimensions were used to predict the water potential that would cause 50 % loss of hydraulic conductivity (Ψ ₅₀). Nothofagus alpina, which mainly grows at sites with low frost frequency, exhibited the largest conduits and the highest mean values for conduit area, fraction of conduit area in the cross-section and hydraulic conductivity, but the lowest wood density. Opposite relationships were found in the plastic N. antarctica, whose xylem seems to be least vulnerable to freezing-induced, but also to drought-induced embolism. Calculated Ψ ₅₀ was highest (least negative) in N. alpina, indicating a relatively high susceptibility to cavitation. The xylem of the thermophilic N. obliqua and of N. dombeyi, which mainly occurs under oceanic climate, but can also survive at sporadically dry and warm sites, is not particularly adapted to periods of drought stress. Across all species, wood density was negatively correlated with the calculated hydraulic conductance. The xylem traits of N. alpina might contribute to its relatively high growth rate and facilitate its spread into forest gaps.     

Mapping of the Ogura fertility restorer gene <Emphasis Type="Italic">Rfo</Emphasis> and development of <Emphasis Type="Italic">Rfo</Emphasis> allele-specific markers in canola (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Ogura cytoplasmic male sterility (CMS) and its corresponding nuclear fertility restorer gene, Rfo, have been introduced from radish to Brassica species by interspecific crosses. Rfo restores male fertility by altering the translational expression of Orf138, a mitochondrial gene, whose expression results in the male sterile phenotype. This system has been extensively investigated and breeding restorer lines for the Ogura CMS has become a major objective for hybrid seed production in many canola breeding programs. In this study, we have sequenced genomic clones of Rfo amplified from a canola restorer line R2000, licensed from INRA, France, and a Dow AgroSciences non-restorer line Nexera 705 using primers designed from the radish Rfo sequence (GenBank accession AJ550021). Sequence alignment revealed three homologous sequences of Rfo. Two of the sequences were present in both R2000 and Nexera 705 but the third one was present only in R2000. These results suggested that the first two sequences could be the homoeologous sequences of Rfo already existing in the canola genome and the third one could be the radish Rfo introduced into canola. Based on the sequence differences between the restorer and non-restorer lines, Rfo allele-specific PCR markers were developed. We also developed a high throughput, Rfo allele-specific Invader^® assay through Third Wave Technologies. Linkage analysis revealed a co-segregation between the allele-specific marker and the phenotypes for fertility restoration. This allele-specific marker has been mapped in the linkage group N19 and proved to be very useful for direct selection of Rfo alleles for fertility restoration during marker-assisted introgression of the Ogura restorer for hybrid development in canola.     

Investigation of systemic control of plant cell division and differentiation in the model of tumor growth in radish

The study addresses the control of plant cell division and differentiation using the model of tumor-forming lines of radish. Expression of the genes involved in control of the cell cycle (CycD3), maintenance of meristematic cell activity (STM, WUS, and KNAT1), and primary response to cytokinin (ARR) was studied in inbred radish lines characterized by tumor growth at different stages of development. The influence of exogenic cytokinin on the expression of the genes of interest is analyzed. The possible role of the CycD3, KNAT1, tSTM, WUS, and ARR5 in tumor formation in radish is discussed.     

Influence of a Permanent Magnetic Field on the Composition and Content of Sugars in Leaves and Storage Roots of Radish Plants of Major Types of Magnetic Orientation

The influence of a weak permanent magnetic field (PMF) with a strength of 400 A/m on the composition and content of sugars was investigated in radish (Raphanus sativus L.) leaves and storage roots of the two major types of magnetic orientation (TMO): North–South (NS TMO) and West–East (WE TMO). Plants were grown in spring and autumn in a greenhouse of the Institute of Plant Physiology, Russian Academy of Sciences. The weak PMF changed the total sugar content in the leaves and storage roots of radish depending on the belonging of the radish plants to the NS or WE type of magnetic orientation, the growing season, and age of plants and the plant organ. The PMF was an environmentally significant factor, since radish plants of different types of magnetic orientation (NS and WE) had a different reaction to the effect of the field related to the peculiarities of their physiological status.     

Defence reactions in the apoplastic proteome of oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> var. <Emphasis Type="Italic">napus</Emphasis>) attenuate <Emphasis Type="Italic">Verticillium longisporum</Emphasis>growth but not disease symptoms

Background

Verticillium longisporum is one of the most important pathogens of Brassicaceae that remains strictly in the xylem during most stages of its development. It has been suggested that disease symptoms are associated with clogging of xylem vessels. The aim of our study was to investigate extracellular defence reactions induced by V. longisporum in the xylem sap and leaf apoplast of Brassica napus var. napus in relation to the development of disease symptoms, photosynthesis and nutrient status.

Results

V. longisporum (strain VL43) did not overcome the hypocotyl barrier until 3 weeks after infection although the plants showed massive stunting of the stem and mild leaf chlorosis. During this initial infection phase photosynthetic carbon assimilation, transpiration rate and nutrient elements in leaves were not affected in VL43-infected compared to non-infected plants. Proteome analysis of the leaf apoplast revealed 170 spots after 2-D-protein separation, of which 12 were significantly enhanced in response to VL43-infection. LS-MS/MS analysis and data base searches revealed matches of VL43-responsive proteins to an endochitinase, a peroxidase, a PR-4 protein and a β-1,3-glucanase. In xylem sap three up-regulated proteins were found of which two were identified as PR-4 and β-1,3-glucanase. Xylem sap of infected plants inhibited the growth of V. longisporum.

Conclusion

V. longisporum infection did not result in drought stress or nutrient limitations. Stunting and mild chlorosis were, therefore, not consequences of insufficient water and nutrient supply due to VL43-caused xylem obstruction. A distinct array of extracellular PR-proteins was activated that might have limited Verticillium spreading above the hypocotyl. In silico analysis suggested that ethylene was involved in up-regulating VL43-responsive proteins.

     

Nucleotide sequence analysis of <Emphasis Type="Italic">S</Emphasis>-locus genes to unify <Emphasis Type="Italic">S</Emphasis> haplotype nomenclature in radish

Radish, belonging to the family Brassicaceae, has a self-incompatibility which is controlled by multiple alleles on the S locus. To employ the self-incompatibility in an F₁ breeding system, identification of S haplotypes is necessary. Since collection of S haplotypes and determination of nucleotide sequences of SLG, SRK, and SCR alleles in cultivated radish have been conducted by different groups independently, the same or similar sequences with different S haplotype names and different sequences with the same S haplotype names have been registered in public databases, resulting in confusion of S haplotype names for researchers and breeders. In the present study, we developed S homozygous lines from radish F₁ hybrid cultivars in Japan and determined the nucleotide sequences of SCR, the S domain and the kinase domain of SRK, and the SLG of a large number of S haplotypes. Comparing these sequences with our previously published sequences, the haplotypes were ordered into 23 different S haplotypes. The sequences of the 23 S haplotypes were compared with S haplotype sequences registered by different groups, and we suggested a unification of these S haplotypes. Furthermore, dot-blot hybridization using SRK allele-specific probes was examined for developing a standard method for S haplotype identification.