Mitogen‐activated protein kinase 3 and 6 regulate Botrytis cinerea‐induced ethylene production in Arabidopsis

Plants challenged by pathogens, especially necrotrophic fungi such as Botrytis cinerea, produce high levels of ethylene. At present, the signaling pathways underlying the induction of ethylene after pathogen infection are largely unknown. MPK6, an Arabidopsis stress‐responsive mitogen‐activated protein kinase (MAPK) was previously shown to regulate the stability of ACS2 and ACS6, two type I ACS isozymes (1‐amino‐cyclopropane‐1‐carboxylic acid synthase). Phosphorylation of ACS2 and ACS6 by MPK6 prevents rapid degradation of ACS2/ACS6 by the 26S proteasome pathway, resulting in an increase in cellular ACS activity and ethylene biosynthesis. Here, we show that MPK3, which shares high homology and common upstream MAPK kinases with MPK6, is also capable of phosphorylating ACS2 and ACS6. In the mpk3 mutant background, ethylene production in gain‐of‐function GVG‐NtMEK2^DD transgenic plants was compromised, suggesting that MPK6 and MPK3 function together to stabilize ACS2 and ACS6. Using a liquid‐cultured seedling system, we found that B. cinerea‐induced ethylene biosynthesis was greatly compromised in mpk3/mpk6 double mutant seedlings. In contrast, ethylene production decreased only slightly in the mpk6 single mutant and not at all in the mpk3 single mutant, demonstrating overlapping roles for these two highly homologous MAPKs in pathogen‐induced ethylene induction. Consistent with the role of MPK3/MPK6 in the process, mutation of ACS2 and ACS6, two genes encoding downstream substrates of MPK3/MPK6, also reduced B. cinerea‐induced ethylene production. The residual levels of ethylene induction in the acs2/acs6 double mutant suggest the involvement of additional ACS isoforms, possibly regulated by MAPK‐independent pathway(s).     

MAPK phosphatase MKP2 mediates disease responses in Arabidopsis and functionally interacts with MPK3 and MPK6

Mitogen‐activated protein kinase (MAPK) cascades have important functions in plant stress responses and development and are key players in reactive oxygen species (ROS) signalling and in innate immunity. In Arabidopsis, the transmission of ROS and pathogen signalling by MAPKs involves the coordinated activation of MPK6 and MPK3; however, the specificity of their negative regulation by phosphatases is not fully known. Here, we present genetic analyses showing that MAPK phosphatase 2 (MKP2) regulates oxidative stress and pathogen defence responses and functionally interacts with MPK3 and MPK6. We show that plants lacking a functional MKP2 gene exhibit delayed wilting symptoms in response to Ralstonia solanacearum and, by contrast, acceleration of disease progression during Botrytis cinerea infection, suggesting that this phosphatase plays differential functions in biotrophic versus necrotrophic pathogen‐induced responses. MKP2 function appears to be linked to MPK3 and MPK6 regulation, as indicated by BiFC experiments showing that MKP2 associates with MPK3 and MPK6 in vivo and that in response to fungal elicitors MKP2 exerts differential affinity versus both kinases. We also found that MKP2 interacts with MPK6 in HR‐like responses triggered by fungal elicitors, suggesting that MPK3 and MPK6 are subject to differential regulation by MKP2 in this process. We propose that MKP2 is a key regulator of MPK3 and MPK6 networks controlling both abiotic and specific pathogen responses in plants.     

产漆酶灰色葡萄孢霉培养条件的研究

通过对培养灰色葡萄孢霉（Botrytis cinerea）不同培养基产漆酶酶活力大小的比较,筛选出了产漆酶灰色葡萄孢霉的最佳培养方法。结果表明：灰色葡萄孢霉在蛋白胨5g/L,酵母提取物20 g/L,蔗糖20 g/L,MgSO4 1.5 g/L,CuSO4 0.006 g/L的培养基中生长最好。最佳的培养条件为：pH值4.9,温度25℃,转速100 r/min。     

Purification and characterization of a 40.8-kDa cutinase in ungerminated conidia of Botrytis cinerea Pers.: Fr

Cytoplasmic soluble proteins from ungerminated conidia of Botrytis cinerea exhibited cutinase activity. A 40.8-kDa cutinase was purified to homogeneity from this crude conidial protein extract. This cutinase does not correspond either to constitutive or to induced lytic cutin enzymes already described by other authors. The possible role of this constitutive cutinase in the induction of other cutinolytic proteins in the early stages of infection of plants by B. cinerea is discussed.     

Decision-making tools for Frankliniella occidentalis management in strawberry: consideration of target markets

The western flower thrips (WFT), Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), a cosmopolitan pest of many crops, is considered a major pest of low tunnel and greenhouse strawberries. The extent of damage to strawberry is unclear because different studies have produced contradictory results. Also, economic thresholds published for WFT in strawberry vary greatly, and most fail to incorporate economic factors. This study was aimed at developing a decision‐making tool for WFT management in strawberries in Israel. Toward this end, economic injury levels (EIL) and economic thresholds were calculated, based on target markets (export vs. domestic). Results indicate that serious infestation of ripe berries may cause a dull, rough appearance, and the fruit may be soft and have a reduced shelf life, rendering it unsuitable for export. Most fruit damage occurred at green and turning‐red stages of development. Two decision‐making tools were developed, one for winter, when WFT populations increase slowly but crop value is high (export market); and the second for spring, when the pest increases rapidly but crop value is low (local markets). Economic thresholds of 10 and 24 WFT/flower were calculated for winter and spring strawberries, respectively, based on direct thrips damage to fruit. This calculation does not take into account the recorded WFT damage to flowers, or its role in facilitating Botrytis cinerea fruit infection. Western flower thrips has proved only an occasional economic pest in Israeli strawberries, and no routine control measures are warranted. Furthermore, augmentative releases of Orius laevigatus or Neoseilus cucumeris against WFT are not justified in this system, because Orius colonizes strawberry fields spontaneously in high numbers when no broad spectrum insecticides are used.     

Diapause dynamics, seasonal phenology, and pupal color dimorphism of Papilio polyxenes in southern Florida, USA

In the European grapevine moth, Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae), it has recently been shown that volatiles emitted from the main host plant, grapevine, are attractive to adult females. Here, using wind tunnel experiments, we tested the attractiveness of various grapevine, Vitis vinifera L. (Vitaceae), plant parts at different phenological stages, including ripe berries infested with the pathogenic fungus Botrytis cinerea (Persoon: Fries) (Sclerotiniaceae) to laboratory‐reared virgin and mated male and female moths. We also tested the attractiveness of the non‐host plant, tansy [Tanacetum vulgare (L.) (Asteraceae)], as flowers and flower volatiles were previously shown to be attractive to L. botrana females in the field. Mated female moths were the only adults to exhibit upwind orientation to grape plant parts in the flight tunnel. The most attractive parts of the grapevine plants were leaves, flower buds, and ripe berries. No attraction was observed to flowers. This corresponds to the phenological stages available when females of the 2–3 generations during a year are present in the field. No attraction was observed to leaves and flowers of tansy.     

Characterisation of a new species of Pythium isolated from a wheat field in northern France and its antagonism towards Botrytis cinerea causing the grey mould disease of the grapevine

A new species, Pythium bifurcatum, isolated from soil samples taken from a wheat field in Lille in northern France is described here. The oomycete occurred thrice out of 50 samples. The type specimen is F-91, which is a slow-growing saprophyte living on vegetable debris and which can be recognised by its antheridial as well as oogonial characteristics, which are different from other known species of Pythium. When grown together with Botrytis cinerea, the causal agent of the grey mould disease of the grapevine, Pythium bifurcatum shows a pronounced antagonism and suppresses its growth. Morphological features of this new species, its antagonism to B. cinerea, the sequences of the ITS region of its nuclear ribosomal DNA, and its comparison with related species are discussed in this article.     

Characterisation of Pythium paroecandrum and its antagonism towards Botrytis cinerea, the causative agent of grey mould disease of grape

Pythium paroecandrum (B-30), an oomycete, was isolated from soil samples taken from a wheat field in Genlis in the Burgundy region of France and was found to check the growth and development of Botrytis cinerea, a serious grapevine pathogen. The oomycete is a fast-growing organism, living on vegetable debris, and can be recognised by its catenulate hyphal swellings, catenulate oogonia, and monoclinous antheridia. When grown together with B. cinerea, the causal agent of the grey mould disease of the grapevine, P. paroecandrum shows a pronounced antagonism and suppresses its growth and its aptitude to provoke the grey mould symptoms. Morphological features of this oomycete, its antagonism to B. cinerea, the sequences of the internal transcribed spacer region of its nuclear ribosomal DNA, and its comparison with related species are discussed in this article.     

Proteinase inhibitors in Nauphoeta cinerea midgut.

Proteinase inhibitors were studied in the midgut of Nauphoeta cinerea Oliv. (Blattoptera: Blaberidae) in experimental conditions, excluding their nutritional origin. One trypsin inhibitor (TI) with M(r) 8,000 and two subtilisin inhibitors (SI1 and SI2) with M(r) 13,000 and 8,000 were detected after fractionation of total protein preparation on Sephadex G-50. Ninety-four percent of both types of inhibitors was located in anterior midgut (AM). TI was 120-fold purified by FPLC-chromatography on Mono Q. Its isoelectric point was 4.3. TI lost a large part of activity in acidic and especially in alkaline medium. TI, SI1, and SI2 effectively inhibited activities of endogenous proteinases from posterior midgut (PM) of the cockroach. A search for inhibitor of endogenous unusual SH-dependent proteinase from AM revealed in AM a new inhibitor with M(r) 18,000. It was also inactivated in alkaline medium and was effective against proteinases from PM along with unusual SH-dependent proteinase from AM. A mechanism of regulation of activity of midgut proteinases is proposed based on pH-stability of inhibitors.     

病原侵染对采后葡萄激素水平的影响

外源ABA处理采后葡萄可显著促进乙烯释放和抑制IAA的生成,加重葡萄落粒。乙烯利对ABA促进作用不明显,但显著抑制IAA和GA3的生成。葡萄感病后组织内源激素水平发生了变化：ABA含量显著增加,乙烯释放率增大,IAA含量显著减少,这种变化趋势在果梗中尤为突出。