DNA markers for identification of Pseudomonas syringae pv. actinidiae.
The specific DNA fragment was screened by RAPD analysis of Pseudomonas syringae pv. actinidiae, as well as similar strains that were isolated from kiwifruits. The primer C24 detected a fragment that is specific in P. syringae pv. actinidiae. This fragment was cloned. The pathovar-specific fragment was detected from a Southern blot analysis of the genomic DNAs of P. syringae pv. actinidiae using the cloned fragment as a probe. The sequence size of the cloned fragment was determined as 675 bp. A DNA Database search suggested that the fragment was a novel one. Approximately 9 kb of a single fragment was detected only in the P. syringae pv. actinidiae by a Southern blot analysis of the genomic DNAs of P. syringae pv. actinidiae. Similar strains were also detected with the use of the cloned fragment as a probe. Since the genomic DNAs were digested with HindIII without a cleavage site, the result reveals that the cloned fragment exists on the genome of P. syringae pv. actinidiae as a single copy. A pair of primers that produced a 492 bp single fragment (only in the strains of P. syringae pv. actinidiae) were synthesized, based on the pathovar-specific sequences of the cloned fragment of P. syringae pv. actinidiae. The development of the primers and probe made it possible to diagnose the bacterial canker infection from leaves or trunks of kiwifruit trees before any symptom appeared on the tree. (+info
Kiwifruit promotes laxation in the elderly.
Numerous anecdotal reports have suggested that kiwifruit (Actinidia deliciosa) has laxative effects. This could be an acceptable dietary supplement, especially for elderly people who often present with constipation. We wished to obtain objective evidence as to whether or not kiwifruit eaten regularly could promote laxation in elderly people. Thirty-eight healthy adults of age > 60 years consumed their normal diet, with or without one kiwifruit per 30 kg bodyweight for three weeks, followed by a 3-week crossover period. Daily records were taken on frequency of defecation and characteristics of the stools. Kiwifruit significantly enhanced all tested measures of laxation in these adults. The regular use of kiwifruit appeared to lead to a bulkier and softer stool, as well as more frequent stool production. Kiwifruit as a natural remedy appears palatable to most of the population and provides improved laxation for elderly individuals who are otherwise healthy. It is likely that a number of factors in the whole fruit are involved, but the nature of the stools suggest fibre is important. This study provides evidence of the potential for improvement in bowel function, health and well-being through changes in diet. (+info
Quantitative analysis of shoot development and branching patterns in Actinidia.
We developed a framework for the quantitative description of Actinidia vine architecture, classifying shoots into three types (short, medium and long) corresponding to the modes of node number distribution and the presence/ absence of neoformed nodes. Short and medium shoots were self-terminated and had only preformed nodes. Based on the cut-off point between their two modes of node number distribution, short shoots were defined as having nine or less nodes, and medium shoots as having more than nine nodes. Long shoots were non-terminated and had a number of neoformed nodes; the total number of nodes per shoot was up to 90. Branching patterns for each parent shoot type were represented by a succession of branching zones. Probabilities of different types of axillary production (latent bud, short, medium or long shoot) and the distributions of length for each branching zone were estimated from experimental data using hidden semi-Markov chain stochastic models. Branching was acrotonic on short and medium parent shoots, with most axillary shoots being located near the shoot tip. For long parent shoots, branching was mesotonic, with most long axillary shoots being located in the transition zone between the preformed and neoformed part of the parent shoot. Although the shoot classification is based on node number distribution there was a marked difference in average (per shoot) internode length between the shoot types, with mean values of 9, 27 and 47 mm for short, medium and long shoots, respectively. Bud and shoot development is discussed in terms of environmental controls. (+info
Modelling kiwifruit budbreak as a function of temperature and bud interactions.
This paper presents two models of budbreak on canes of 'Hayward' kiwifruit (Actinidia deliciosa). A conventional 'chill unit' (CU) type model is compared with an alternative 'loss of potential' (LOP) approach, which assumes that the number of buds developing in spring depends on climate and node position-dependent bud-to-bud interactions that vary in duration and intensity. Both models describe how temperature, and application of a dormancy-breaking chemical, determine the overall amount of budbreak for whole canes. However, the LOP model does so by describing patterns of budbreak along canes. To do this, the cumulative influence of distal neighbours is assumed to cause a progressive fall in the capacity for bud development over the autumn-winter period, an influence that gets stronger as temperature rises. The LOP model also assumes that the rate of decline varies along the cane, as a function of some inherent bud property. These two factors mean that buds towards the base of the cane break less often under the suppressive influence of distal neighbours, while low temperature ('chilling') increases budbreak by diminishing the intensity of suppression relative to bud development rate. Under this scenario, dormancy-breaking chemicals (such as hydrogen cyanamide, HC) enhance budbreak by diminishing the duration of suppression. Models were calibrated using daily temperature series and budbreak proportion data from a multi-year regional survey, and were then tested against independent data sets. Both models were run from a fixed start date until the time budbreak was almost complete, or until a standard date. The fitted models described 87 % of variation in amount of budbreak due to site, year, HC and node position effects in the original data set. Results suggest that the correlation between chilling and the amount of budbreak can be interpreted as a population-based phenomenon based on interaction among buds. (+info
A case of chloroplast heteroplasmy in kiwifruit (Actinidia deliciosa) that is not transmitted during sexual reproduction.
We report the first case of plastid chimera within the Actinidia genus, where plastid inheritance was believed to be paternal. The heterogeneity of chloroplast DNA observed in the hexaploid Actinidia deliciosa cultivar D uno involves the presence or absence of a particular MspI restriction site in the region between the psbC gene and the tRNA-Ser(UGA) gene. The heterogeneity was first observed using restriction fragment length polymorphism and then confirmed through cloning and sequencing. The analysis of the cloned fragments revealed the presence of two haplotypes: the most frequent type was found in 123 (88.5%) out of a total of 139 colonies screened. Partial sequences of the psbC-trnS fragment from both haplotypes revealed that the polymorphism occurs within the coding region of the psbC gene and consists of a synonymous transition. A contamination-free cross involving D uno as the male parent produced only plants characterized by the most frequent haplotype, indicating either selection bias against the rare type or more likely fixation of the frequent type in tissues leading to the formation of the male gametes. The MspI restriction profiles performed on various tissues suggest that the rarer type is absent from the histogenic layer LII and that D uno is a periclinal plastid chimera. (+info
A one-step organelle capture: gynogenetic kiwifruits with paternal chloroplasts.
Androgenesis, the development of a haploid embryo from a male nucleus, has been shown to result in the instantaneous uncoupling of the transmission of the organelle and nuclear genomes (with the nuclear genome originating from the male parent only and the organelle genomes from the female parent). We report, for the first time, uncoupling resulting from gynogenesis, in Actinidia deliciosa (kiwifruit), a plant species known for its paternal mode of chloroplast inheritance. After pollen irradiation, transmission of nuclear genes from the pollen parent to the progeny was inhibited, but transmission of the chloroplast genome was not. This demonstrates that plastids can be discharged from the pollen tube into the egg with little or no concomitant transmission of paternal nuclear genes. Such events of opposite inheritance of the organelle and nuclear genomes must be very rare in nature and are unlikely to endanger the long-term stability of the association between the different genomes of the cell. However, they could lead to incongruences between organelle gene trees and species trees and may constitute an alternative to the hybridization/introgression scenario commonly invoked to account for such incongruences. (+info
Chloroplast inheritance patterns in Actinidia hybrids determined by single stranded conformation polymorphism analysis.
The inheritance patterns of the chloroplast genomes of the Actinidia hybrids A. eriantha (male parent) x A. chinensis (female parent) and A. chinensis (male parent) x A. melanandra (female parent) were analyzed using single-strand conformation polymorphism (SSCP) analysis of the trnL-trnF and psbA-trnH intergenic spacers. This showed that the artificial hybrids between A. eriantha and A. chinensis all had the haplotype of their male parent. Alignment of the sequences of A. eriantha and A. chinensis revealed four substitutions and one insertion (GATTC) in trnL-trnF and two substitutions in psbA-trnH. In contrast, the haplotypes of the artificial hybrids between A. chinensis and A. melanandra had the same patterns as their female parent. Alignment of the entire region of A. chinensis and A. melanandra revealed 12 substitutions: 1 in trnL-trnF and 11 in psbA-trnH. However, no sequence variation in the trnL-trnF and psbA-trnH intergenic spacers was found. We have developed a simple screening method for detecting the inheritance patterns of Actinidia chloroplast DNA haplotypes using SSCP analysis of the trnL-trnF and psbA-trnH intergenic spacers. Our findings indicate that the inheritance of the chloroplast genome in Actinidia hybrids differs according to the species selected. (+info
Pectin methylesterase inhibitor.
Pectin methylesterase (PME) is the first enzyme acting on pectin, a major component of plant cell wall. PME action produces pectin with different structural and functional properties, having an important role in plant physiology. Regulation of plant PME activity is obtained by the differential expression of several isoforms in different tissues and developmental stages and by subtle modifications of cell wall local pH. Inhibitory activities from various plant sources have also been reported. A proteinaceous inhibitor of PME (PMEI) has been purified from kiwi fruit. The kiwi PMEI is active against plant PMEs, forming a 1:1 non-covalent complex. The polypeptide chain comprises 152 amino acid residues and contains five Cys residues, four of which are connected by disulfide bridges, first to second and third to fourth. The sequence shows significant similarity with the N-terminal pro-peptides of plant PME, and with plant invertase inhibitors. In particular, the four Cys residues involved in disulfide bridges are conserved. On the basis of amino acid sequence similarity and Cys residues conservation, a large protein family including PMEI, invertase inhibitors and related proteins of unknown function has been identified. The presence of at least two sequences in the Arabidopsis genome having high similarity with kiwi PMEI suggests the ubiquitous presence of this inhibitor. PMEI has an interest in food industry as inhibitor of endogenous PME, responsible for phase separation and cloud loss in fruit juice manufacturing. Affinity chromatography on resin-bound PMEI can also be used to concentrate and detect residual PME activity in fruit and vegetable products. (+info