Changes in motility of Pythium zoospores induced by calcium and calcium-modulating drugs

Donaldson, S. P.; Deacon, J.W.

doi:10.1016/s0953-7562(09)81166-0

Cited by 44 publications

(26 citation statements)

References 24 publications

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“…Little effect was noted when trifluoroperazine was added to zoospores, but most lysed when vortexed in an attempt to induce encystment. Both compounds also altered the directionality of swimming as reported previously (10).…”

Section: Judelson and Roberts Eukaryot Cellsupporting

confidence: 83%

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Novel Protein Kinase Induced during Sporangial Cleavage in the Oomycete Phytophthora infestans

Judelson

Roberts

2002

Eukaryot Cell

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A study of the effect of inhibitors on zoospore development in Phytophthora infestans demonstrated the involvement of protein kinases and calcium and led to the discovery of a gene induced during zoosporogenesis that encoded a protein resembling Ca ؉2 -and calmodulin-regulated serine/threonine protein kinases. The calcium channel blocker verapamil and the calmodulin antagonist trifluoroperazine inhibited zoosporogenesis and encystment. The protein kinase inhibitors K-252a and KN-93 inhibited zoospore release, encystment, and cyst germination, and K-252a reduced zoospore viability. In contrast, the inhibitors had minor or no effects on sporangia directly germinating in media. Spurred by these findings, a survey of putative protein kinase genes was performed to identify any that were up-regulated during zoosporogenesis. A kinase-encoding gene was identified for which mRNA accumulation was first detected soon after chilling sporangia in water, conditions that induce sporangial cytoplasm to cleave and release zoospores. The transcript persisted in motile zoospores and in germinated cysts but was not detected in other tissues, including hyphae, hyphae placed in water, or directly germinating sporangia. The structure of the predicted protein was novel, as its C-terminal region, which binds calmodulin in related proteins, was unusually short. Concentrations of actinomycin D previously used in experiments that suggested that de novo transcription was not needed for zoosporogenesis or encystment only partially inhibited transcription of the kinase gene, probably due to poor uptake into sporangia.Dispersal by means of spores is a common feature of the life cycle of many lower eukaryotes. This includes the oomycetes, which encompass many important plant pathogens, including Phytophthora, Pythium, and the downy mildews. Oomycetes lack taxonomic affinity with the so-called true fungi (i.e., ascomycetes and basidiomycetes), instead being related to diatoms and brown algae (2, 15). The asexual sporangia of oomycetes either germinate directly through a germ tube or indirectly by releasing biflagellate zoospores. Many species germinate through either pathway, while others produce only zoospores and some germinate only directly (12,22,26). For species displaying both modes of germination, zoospores are considered most important for dispersal and host infection.One species exhibiting this duality in germination behavior is Phytophthora infestans, which causes late blight of potato and tomato. Sporangia form on sporangiophores that emerge from infected plant tissue or from hyphae on artificial media. As with other oomycetes, the sporangia of P. infestans are multinucleate, nondesiccated, and metabolically active. Germination becomes possible once sporangia detached from sporangiophores encounter liquid. Indirect germination predominates in the absence of nutrients and at cool temperatures, typically below 12°C (30). In contrast, direct germination is favored by higher temperatures and nutrients. Indirect germination takes about 1 h...

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Section: Judelson and Roberts Eukaryot Cellsupporting

confidence: 83%

“…The effects of kinase inhibitors on these pathways have not been previously reported, but the other compounds have been tested against a subset of the stages in Phytophthora or Pythium (8,10,11,27,37,38). The inhibitors were added to sporangia 5 min before …”

Section: Effects Of Inhibitors On Differentiationmentioning

confidence: 99%

Novel Protein Kinase Induced during Sporangial Cleavage in the Oomycete Phytophthora infestans

Judelson

Roberts

2002

Eukaryot Cell

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“…For example, they encysted very quickly, a phenomenon that could be due to inappropriate activation of calcium signaling (14,26,54). Zoospores can be induced to encyst by a variety of external stimuli, including mechanical shock, pectin, calcium, and isoflavones (17,25,43). Calmodulin is a typical calcium sensor, which binds calcium and activates downstream kinases and phosphatases.…”

Section: Discussionmentioning

confidence: 99%

“…Already in 1981 it was reported that zoospores swim more smoothly in the presence of an attractant and turn more frequently in the presence of a repellent (9). The importance of external calcium for the swimming behavior of zoospores also is well known (9,17,23), but how the external stimuli are perceived and transmitted into the zoospores is far less understood. This study on P. sojae and that of Latijnhouwers et al (33) on P. infestans clearly demonstrate that zoospore motility is controlled by G␣-mediated signaling.…”

Section: Discussionmentioning

confidence: 99%

A Phytophthora sojae G-Protein α Subunit Is Involved in Chemotaxis to Soybean Isoflavones

et al. 2008

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For the soybean pathogen Phytophthora sojae, chemotaxis of zoospores to isoflavones is believed to be critical for recognition of the host and for initiating infection. However, the molecular mechanisms underlying this chemotaxis are largely unknown. To investigate the role of G-protein and calcium signaling in chemotaxis, we analyzed the expression of several genes known to be involved in these pathways and selected one that was specifically expressed in sporangia and zoospores but not in mycelium. This gene, named PsGPA1, is a single-copy gene in P. sojae and encodes a G-protein ␣ subunit that shares 96% identity in amino acid sequence with that of Phytophthora infestans. To elucidate the function, expression of PsGPA1 was silenced by introducing antisense constructs into P. sojae. PsGPA1 silencing did not disturb hyphal growth or sporulation but severely affected zoospore behavior, including chemotaxis to the soybean isoflavone daidzein. Zoospore encystment and cyst germination were also altered, resulting in the inability of the PsGPA1-silenced mutants to infect soybean. In addition, the expressions of a calmodulin gene, PsCAM1, and two calcium-and calmodulin-dependent protein kinase genes, PsCMK3 and PsCMK4, were increased in the mutant zoospores, suggesting that PsGPA1 negatively regulates the calcium signaling pathways that are likely involved in zoospore chemotaxis.The ability to recognize host signals may be critical for the behavior of plant pathogens or symbionts. Chemotaxis to a host-specific signal has been described for several plant-microbe associations (11,43,44). In plant-pathogenic Agrobacterium species, for example, chemotaxis to plant exudates appears to enhance virulence on soil-grown plants (24). In nitrogen-fixing bacteria, such as Rhizobium and Bradyrhizobium species, expression of nodulation genes is induced by flavones and isoflavones (19), which are secondary metabolites present in seeds of leguminous plants and are exuded by the roots of those plants. Chemotaxis of zoospores of the oomycete pathogen Phytophthora sojae to isoflavones is believed to be an important step in the disease cycle, particularly in recognition of the host and in initiating infection (42,43). P. sojae is a devastating pathogen on soybean that causes "damping off" of seedlings and root rot on older plants. The annual loss worldwide is estimated to be $1 billion to $2 billion (49).P. sojae zoospores are specifically attracted to the isoflavones daidzein and genistein at concentrations of as low as 10 nM (43). Since zoospores of other Phytophthora spp. are not attracted to these compounds, chemotaxis may be part of the mechanism that determines host range (43). Besides motile zoospores, hyphal germ tubes of P. sojae also respond chemotropically to soybean isoflavones (42, 51). Although there are indications that calcium influx plays a role in chemotaxis (12), the signal transduction pathways governing the response of P. sojae to isoflavones are largely unknown. The first step in unraveling these pathways is identif...

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“…A velocidade média atingida por um zoósporo varia de 100 a 200 µm/s (DONALDSON; DEACON, 1993;van WEST, 2002). Ao atingir a superfície das raízes, acabam por encistar-se e, a partir, dos cistos aderidos às raízes, são formadas hifas, que começam a penetrar diretamente nestas por meio da emissão do tubo germinativo.…”

Section: Introductionunclassified

<i>Phytophthora nicotianae</i>: ação de meios de cultura e da qualidade da luz no crescimento e esporulação e aspectos fisiológicos e bioquímicos da interação com porta-enxertos cítricos

Santos¹,

Júnior²

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A Dona Maria Oliveira, mulher guerreira e batalhadora, que sempre fez, com garra, a limpeza dos espaços físicos do Departamento de Fitopatologia e Nematologia e da Biblioteca;Aos meus queridos amigos, parentes e conterrâneos do Município de Primavera-PA;A todos aqueles que, direta ou indiretamente, colaboraram para a realização dessa tese. RESUMOPhytophthora nicotianae: ação de meios de cultura e da qualidade da luz no crescimento e esporulação e aspectos fisiológicos e bioquímicos da interação com porta-enxertos cítricos A citricultura brasileira apresenta números bastante significativos e expressivos, refletindo a grande importância social e econômica que essa atividade agrícola e industrial tem para a economia do país. O Brasil se destaca como o maior produtor de laranja do mundo. As plantas cítricas podem ser produzidas e multiplicadas de várias formas e a enxertia é a forma de propagação vegetativa mais utilizada comercialmente no Brasil. Dentre os porta-enxertos mais empregados, sobressaem-se o citrumeleiro Swingle e a tangerineira Sunki. Apesar das vantagens presentes nesses dois genótipos, a produção deles está sendo limitada por doenças causadas por fungos e estraminipilas. Em citros, as diversas espécies de Phytophthora são responsáveis pelas doenças gomose e podridões, principalmente de radicelas. P. nicotianae é a espécie que mais afeta as plantas cítricas no Brasil. Não obstante a grande importância de P. nicotianae para os porta-enxertos, alguns mecanismos de resistência ou susceptibilidade ainda requerem mais investigações cientificas. O presente trabalho visa a elucidação de alguns mecanismos de resistência dos citros a P. nicotianae, por meio de estudos fisiológicos e bioquímicos dos porta-enxertos, além da ação de meios de cultura e da qualidade da luz no estudo da fisiologia desse estraminipila. Para isso realizou-se a detecção de alguns equivalentes de compostos fenólicos através da técnica HPLC e o comportamento do genótipo resistente frente à possível inibição da síntese de compostos fenólicos através do tratamento das raízes do porta-enxerto Swingle com Pro-Ca; avaliou-se a atração de zoósporos de P. nicotianae por exsudatos radiculares provenientes dos dois porta-enxertos com o uso de uma armadilha adaptada; verificou-se o comportamento do zoósporo, a motilidade e a zoosporogênese frente à ação de vários compostos fenólicos e testou-se a ação de diferentes meios de culturas e da qualidade da luz no crescimento micelial e na esporulação de P. nicotianae. Os resultados revelaram que a tangerineira Sunki possui maiores quantidades de equivalentes em apigenina que o citrumeleiro Swingle nos dois períodos de avaliação, para o HPLC. O porta-enxerto resistente apresentou mais equivalentes de ácido clorogênico que o genótipo susceptível. Quanto ao Pro-Ca, os equivalentes de compostos fenólicos em raízes de plântulas do citrumeleiro Swingle não diferiram daquelas plantas tratadas com água. O Pro-Ca não inibiu e não desativou a síntese de compostos fenólicos. O uso do anticorpo contra a elicitina ...

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Changes in motility of Pythium zoospores induced by calcium and calcium-modulating drugs

Cited by 44 publications

References 24 publications

Novel Protein Kinase Induced during Sporangial Cleavage in the Oomycete Phytophthora infestans

Novel Protein Kinase Induced during Sporangial Cleavage in the Oomycete Phytophthora infestans

A Phytophthora sojae G-Protein α Subunit Is Involved in Chemotaxis to Soybean Isoflavones

<i>Phytophthora nicotianae</i>: ação de meios de cultura e da qualidade da luz no crescimento e esporulação e aspectos fisiológicos e bioquímicos da interação com porta-enxertos cítricos

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