Natively oxidized amino acid residues in the spinach cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript><Emphasis Type="Italic">6</Emphasis></Subscript><Emphasis Type="Italic">f</Emphasis> complex

The cytochrome b ₆ f complex of oxygenic photosynthesis produces substantial levels of reactive oxygen species (ROS). It has been observed that the ROS production rate by b ₆ f is 10–20 fold higher than that observed for the analogous respiratory cytochrome bc₁ complex. The types of ROS produced (O₂^{??, 1}O₂, and, possibly, H₂O₂) and the site(s) of ROS production within the b ₆ f complex have been the subject of some debate. Proposed sources of ROS have included the heme b _p , PQ _p ^?? (possible sources for O₂^??), the Rieske iron–sulfur cluster (possible source of O₂^?? and/or ¹O₂), Chl a (possible source of ¹O₂), and heme c _n (possible source of O₂^?? and/or H₂O₂). Our working hypothesis is that amino acid residues proximal to the ROS production sites will be more susceptible to oxidative modification than distant residues. In the current study, we have identified natively oxidized amino acid residues in the subunits of the spinach cytochrome b ₆ f complex. The oxidized residues were identified by tandem mass spectrometry using the MassMatrix Program. Our results indicate that numerous residues, principally localized near p-side cofactors and Chl a, were oxidatively modified. We hypothesize that these sites are sources for ROS generation in the spinach cytochrome b ₆ f complex.     

<Emphasis Type="Italic">ADH</Emphasis> and <Emphasis Type="Italic">PDC</Emphasis> genes involved in tannins coagulation leading to natural de-astringency in Chinese pollination constant and non-astringency persimmon (<Emphasis Type="Italic">Diospyros kaki</Emphasis> Thunb.)

Pollination constant non-astringency (PCNA)-type persimmons are the most desirable cultivar because the fruit loses astringency naturally and does not require any treatments for edibility. The mechanism of natural astringency loss in Chinese PCNA (C-PCNA)-type persimmon is probably related to the coagulation of soluble tannins into insoluble tannins, which is quite different from that in the Japanese PCNA (J-PCNA) type. In this work, three types of persimmon cultivars were sampled: ‘Luotian-tianshi’ (C-PCNA), ‘Maekawa-jirou’ (J-PCNA), and ‘Mopanshi’ (pollination constant astringent (PCA)) were sampled. Three DkADH and four DkPDC genes were isolated from C-PCNA plants. Three candidate genes for soluble tannins coagulation identified in C-PCNA fruit (DkADH1, DkPDC1, and DkPDC2) were characterized through combined analysis of spatiotemporal expression patterns and tannin and acetaldehyde contents during fruit development. Transient over-expression in persimmon leaves showed that DkADH1 and DkPDC2 led to a significant decrease in the levels of soluble tannins in infiltrated leaves. These results indicated that DkADH and DkPDC genes should be considered key genes for natural astringency loss in C-PCNA types.     

Identification of 21 novel <Emphasis Type="Italic">S-RNase</Emphasis> alleles and determination of <Emphasis Type="Italic">S</Emphasis>-genotypes in 66 loquat (<Emphasis Type="Italic">Eriobotrya</Emphasis>) accessions

As observed in other self-incompatible species in the Pyrinae subtribe, loquat (Eriobotrya japonica) demonstrates gametophytic self-incompatibility that is controlled by the S-locus, which encodes a polymorphic stylar ribonuclease (S-RNase). This allows the female reproductive organ (style) to recognize and reject the pollen from individuals with the same S-alleles, but allows the pollen from individuals with different S-alleles to effect fertilization. The S-genotype is therefore an important consideration in breeding strategies and orchard management. In an attempt to optimize the selection of parental lines in loquat production, the S-RNase alleles of 35 loquat cultivars and their 26 progeny, as well as five wild loquat species, were identified and characterized in this study. The best pollinizer cultivar combinations were also explored. A total of 28 S-alleles were detected, 21 of which constituted novel S-RNase alleles. The S-haplotypes S₂ and S₆ were the most frequent, followed by S ₂₉ , S ₃₁ , S ₅ , S ₂₄ , S ₂₈ , S ₃₃ , S ₃₄ , S ₃₂ , and S ₁₅ , while the rare alleles S ₁ , S ₉ , S ₁₄ , S ₁₆ , S ₁₇ , S ₁₈ , S ₁₉ , S ₂₀ , S ₂₁ , S ₂₂ , S ₂₃ , S ₂₇ , and S ₃₅ were only observed in one of the accessions tested. Moreover, the S-genotypes of five wild loquat species (E. prinoides, E. bengalensis, E. prinoides var. dadunensis, E. deflexa, and E. japonica) are reported here for the first time. The results will not only facilitate the selection of suitable pollinators for optimal orchard management, but could also encourage the crossbreeding of wild loquat species to enhance the genetic diversity of loquat cultivars.     

Genetic mapping reveals a candidate gene (<Emphasis Type="Italic">ClFS1</Emphasis>) for fruit shape in watermelon (<Emphasis Type="Italic">Citrullus lanatus</Emphasis> L.)

Key message

A 159 bp deletion in ClFS1 gene encoding IQD protein is responsible for fruit shape in watermelon.

Abstract

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is known for its rich diversity in fruit size and shape. Fruit shape has been one of the major objectives of watermelon breeding. However, the candidate genes and the underlying genetic mechanism for such an important trait in watermelon are unknown. In this study, we identified a locus on chromosome 3 of watermelon genome controlling fruit shape. Segregation analysis in F₂ and BC₁ populations derived from a cross between two inbred lines “Duan125” (elongate fruit) and “Zhengzhouzigua” (spherical fruit) suggests that fruit shape of watermelon is controlled by a single locus and elongate fruit (OO) is incompletely dominant to spherical fruit (oo) with the heterozygote (Oo) being oval fruit. GWAS profiles among 315 accessions identified a major locus designated on watermelon chromosome 3, which was confirmed by BSA-seq mapping in the F₂ population. The candidate gene was mapped to a region 46 kb on chromosome 3. There were only four genes present in the corresponding region in the reference genome. Four candidate genes were sequenced in this region, revealing that the CDS of Cla011257 had a 159 bp deletion which resulted in the omission of 53 amino acids in elongate watermelon. An indel marker was derived from the 159 bp deletion to test the F₂ population and 105 watermelon accessions. The results showed that Cla011257 cosegregated with watermelon fruit shape. In addition, the Cla011257 expression was the highest at ovary formation stage. The predicted protein of the Cla011257 gene fitted in IQD protein family which was reported to have association with cell arrays and Ca²⁺-CaM signaling modules. Clear understanding of the genes facilitating the fruit shape along with marker association selection will be an effective way to develop new cultivars.

     

Dietary Flexibility and Feeding Strategies of <Emphasis Type="Italic">Eulemur</Emphasis>: A Comparison with <Emphasis Type="Italic">Propithecus</Emphasis>

Despite the great variety of habitats in Madagascar, Eulemur has successfully populated most forested habitats on the island. Although the high dietary flexibility of Eulemur is often credited as one of the drivers of its evolutionary success, other behavioral evidence suggests a limited capacity for dietary switching. To shed light on the feeding strategies of Eulemur, we compared the dietary flexibility between populations of this genus with that of another widespread lemur taxon, Propithecus. We hypothesized that Eulemur would show greater dietary flexibility than Propithecus, which has a digestive system specialized for folivory, and that Eulemur living in dry forests would switch its diet from fruit to other food seasonally. To examine these hypotheses, we performed a phylogenetic least-squares analysis on 10 populations of Eulemur and 7 of Propithecus to assess the contribution of environmental variables and body mass on their dietary flexibility while controlling for phylogenetic relatedness. Eulemur relied heavily on fruit and did not show large variations in primary food over the year. Propithecus consumed leaves and fruits equally and exhibited considerable flexibility across seasons. Therefore, in contrast to our predictions, the anatomical specialization for fiber digestion heightens dietary flexibility in Propithecus. At the intrageneric level, we found similar ecogeographic variation; populations of both genera with heavier body mass consumed more fruit. As we predicted, Eulemur in drier habitats switched the diet from fruit to alternative food more frequently. To compensate for low dietary flexibility, Eulemur mostly adopts a power-feeding strategy by which it increases energy expenditure to acquire patchily distributed fruit resources.     

Over-expressing a UDP-glucosyltransferase gene (<Emphasis Type="Italic">Ta-UGT</Emphasis><Subscript><Emphasis Type="Italic">3</Emphasis></Subscript>) enhances <Emphasis Type="Italic">Fusarium</Emphasis> Head Blight resistance of wheat

Wheat Fusarium Head Blight (FHB), mainly caused by Fusarium graminearum (F.g), is a destructive fungal disease worldwide. FHB can not only cause considerable reduction in yield, but more seriously, can contaminate grain by trichothecene toxins released by the fungus. Here, we report new insights into the function and underlying mechanisms of a UDP-glycosyltransferase gene, Ta-UGT ₃ , that is involved in FHB resistance in wheat. In our previous study, Ta-UGT ₃ was found to enhance host tolerance against deoxynivalenol (DON) in Arabidopsis. In this study, four transgenic lines over-expressing Ta-UGT ₃ in a FHB highly susceptible wheat variety, Alondra’s, were obtained and characterized. 3 years of assays using single floret inoculation with F.g indicated that all four transgenic lines exhibited significantly enhanced type II resistance to FHB and less DON accumulation in the grains compared to the untransformed control. Histological observation using GFP labelled F.g was in agreement with the above test results since over-expression of Ta-UGT ₃ dramatically inhibited expansion of F.g. To explore the putative mechanism of resistance mediated by Ta-UGT ₃ , microarray analysis, qRT-PCR and hormone measurements were performed. Microarray analysis showed that DON up-regulated genes, such as TaNPR1, in the susceptible control, and down-regulated genes in F.g inoculated transgenic lines, while qRT-PCR showed that some defence related genes were up-regulated in F.g inoculated transgenic lines. Ta-UGT ₃ over-expression also changed the contents of the endogenous hormones SA and JA in the spikes. These data suggest that Ta-UGT ₃ positively regulates the defence responses to F.g, perhaps by regulating defence-related and DON-induced downstream genes.     

Genetics and fine mapping of a yellow-green leaf gene (<Emphasis Type="Italic">ygl</Emphasis>-<Emphasis Type="Italic">1</Emphasis>) in cabbage (<Emphasis Type="Italic">Brassica oleracea</Emphasis> var. <Emphasis Type="Italic">capitata</Emphasis> L.)

Cabbage (Brassica oleracea var. capitata L.) is one of the most popular cultivated vegetables worldwide. Cabbage has rich phenotypic diversity, including plant height, head shape, head color, leaf shape and leaf color. Leaf color plays an important role in cabbage growth and development. At present, there are few reports on fine mapping of leaf color mutants in B. oleracea. In this study, a naturally occurring yellow-green leaf cabbage mutant (YL-1), derived from the self-pollinated progenies of the hybrid ‘Hosom’, was used for inheritance analysis and gene mapping. Segregation populations including F₂ and BC₁ were generated from the cross of two inbred lines, YL-1 and 01–20. Genetic analysis with the F₂ and BC₁ populations demonstrated that the yellow-green leaf color was controlled by a single recessive nuclear gene, ygl-1. Insertion–deletion (InDel) markers, designed based on the parental re-sequencing data, were used for the preliminary mapping with BSA (bulked segregant analysis) method. A genetic map constructed with 15 InDels indicated that ygl-1 was located on chromosome C01. The ygl-1 gene is flanked by InDel markers ID2 and M8, with genetic distances of 0.4 cM and 0.35 cM, respectively. The interval distance between two markers is 167 kb. Thus, it enables us to locate the ygl-1 gene for the first time in B. oleracea. This study lays the foundation for candidate gene prediction and ygl-1gene cloning.     

Dynamic changes in energy metabolism and electron transport of photosystem II in <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> infested by nymphs of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Middle East-Asia Minor 1)

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) infestation adversely affected photosynthesis of host plants. In the current study, chlorophyll a fluorescence was measured to determine the effects of MEAM1 nymph infestation of tobacco local and systemic leaves on energy metabolism and electron transport of photosystemII(PSII). The results showed that the density of PSII reaction centres per excited cross section (CS) (RC/CS) of infested and systemic leaves was reduced at 14 and 20 days. In systemic leaves, the number of PSII closed reaction centres (1-qP) increased significantly at 14 and 20 days. Absorption flux per Q_A^? reducing PSII reaction centre (RC) (ABS/RC), trapped energy flux per RC (TRo/RC), and electron transport per RC (ETo/RC) of infested and systemic leaves increased with MEAM1 nymph infestation. The most obvious increase in absorption flux per CS (ABS/CSo) and trapped energy flux per CS (TRo/CSo) of infested and systemic leaves occurred at 14 days. MEAM1 nymph infestation significantly reduced the energy required for PSII Q_A to be completely reduced (Sm) in tobacco leaves. These results suggested that MEAM1 nymph infestation caused changes in light-harvesting antenna system and deactivation of the reaction centre, resulting in the reduction of photons absorbed by reaction centres per unit area. MEAM1 nymph infestation, particularly the 3rd instar nymphs, decreased light utilization ability and increased excess excitation energy in tobacco leaves. With MEAM1 nymph infestation, the relative electron transport capacity of the entire electron transport chain decreased, and more light energy was used to reduce Q_A.     

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.

     

Strains of <Emphasis Type="Italic">Bacillus</Emphasis> ssp. regulate wheat resistance to <Emphasis Type="Italic">Septoria nodorum</Emphasis> Berk.

The ability of Bacillus subtilis Cohn and Bacillus thuringiensis Berliner to induce systemic resistance in wheat plants to the casual agent of Septoria nodorum Berk., blotch has been studied. It has been shown that strains of Bacillus ssp. that possess the capacity for endophytic survival have antagonistic activity against this pathogen in vitro. A reduction of the degree of Septoria nodorum blotch development on wheat leaves under the influence of Bacillus spp. was accompanied by the suppression of catalase activity, an increase in peroxidase activity and H₂O₂ content, and expression of defence related genes such us PR-1, PR-6, and PR-9. It has been shown that B. subtilis 26 D induces expression levels of wheat pathogenesis-related (PR) genes which marks a SA-dependent pathway of sustainable development and that B. thuringiensis V-5689 and V-6066 induces a JA/ET-dependent pathway. These results suggest that these strain Bacillus spp. promotes the formation of wheat plant resistance to S. nodorum through systemic activation of the plant defense system. The designed bacterial consortium formed a complex biological response in wheat plants infected phytopathogen.     

A review of the history of research and control of <Emphasis Type="Italic">Rhipicephalus</Emphasis> (<Emphasis Type="Italic">Boophilus</Emphasis>) <Emphasis Type="Italic">microplus</Emphasis>, babesiosis and anaplasmosis in Uruguay

The effect of five constant temperatures (16, 20, 24, 28 and 32 °C) on the development, survival and reproduction of Tetranychus cinnabarinus (Boisduval) [=?Tetranychus urticae Koch (red form)] fed on cassava leaves was examined in the laboratory at 85% relative humidity. Development time of various immature stages decreased with increasing temperature, with total egg-to-adult development time varying from 27.7 to 6.7 days. The lower thermal threshold for development was 10.8 °C and the thermal constant from egg to adult was 142.4 degree-days. Pre- and post-oviposition period and female longevity all decreased as temperature increased. The longest oviposition period was observed at 20 °C with 20.4 days. Under different temperatures, mated females laid, on average, 1.0, 2.9, 4.7, 4.7 and 4.9 eggs per day, respectively. The maximum fecundity (81.5 eggs per female) was at 28 °C and the intrinsic rate of increase (r _m ) was highest (0.25) at 32 °C. The results of this study indicate that T. cinnabarinus population could increase rapidly when cassava leaves serve as a food source. At the appropriate temperature T. cinnabarinus could seriously threaten growth of cassava.