Gene expression changes during asexual sporulation by the late blight agent Phytophthora infestans occur in discrete temporal stages

Abstract

Transcriptional changes during asexual sporangia formation by the late blight pathogen Phytophthora infestans were identified using microarrays representing 15,646 genes and RNA from sporulation time-courses, purified spores, and sporulation-defective strains. Results were confirmed by reverse transcription-polymerase chain reaction analyses of sporulation on artificial media and infected tomato. During sporulation, about 12% of genes were up-regulated compared to vegetative hyphae and 5% were down-regulated. The most prevalent induced genes had functions in signal transduction, flagella assembly, cellular organization, metabolism, and molecular or vesicular transport. Distinct patterns of expression were discerned based on the kinetics of mRNA induction and their persistence in sporangia. For example, most flagella-associated transcripts were induced very early in sporulation and maintained in sporangia, while many participants in metabolism or small molecule transport were also induced early but had low levels in sporangia. Data from this study are a resource for understanding sporogenesis, which is critical to the pathogenic success of P. infestans and other oomycetes.

Phytophthora nicotianae transformants lacking dynein light chain 1 produce non-flagellate zoospores

“…secretory vesicles) destined for Phytophthora zoospores are synthesized during sporangium formation (sporangiogenesis), including a number of flagellar surface components (Cope and Hardham, 1994;Dearnaley et al, 1996;Hardham and Hyde, 1997). The expression of genes encoding proteins stored or functioning in zoospores has been shown to occur after the induction of sporulation (Judelson et al, 2008(Judelson et al, , 2009Marshall et al, 2001b;Robold and Hardham, 2005). Our demonstration of the up-regulation of expression of the DLC1 gene in P. cinnamomi and P. nicotianae during sporulation is in accord with the results of a recent study of the P. infestans sporulation transcriptome (Judelson et al, 2009).…”

“…The expression of genes encoding proteins stored or functioning in zoospores has been shown to occur after the induction of sporulation (Judelson et al, 2008(Judelson et al, , 2009Marshall et al, 2001b;Robold and Hardham, 2005). Our demonstration of the up-regulation of expression of the DLC1 gene in P. cinnamomi and P. nicotianae during sporulation is in accord with the results of a recent study of the P. infestans sporulation transcriptome (Judelson et al, 2009). While the increase in P. cinnamomi appears to be more modest, in P. nicotianae, qPCR measurements indicated an approximately 18-fold increase in PnDLC1 transcript levels coincident with the development of sporangia in the cultures.…”

“…While the increase in P. cinnamomi appears to be more modest, in P. nicotianae, qPCR measurements indicated an approximately 18-fold increase in PnDLC1 transcript levels coincident with the development of sporangia in the cultures. In P. infestans, genes encoding a number of flagellar proteins are up-regulated during sporangiogenesis, including a 50-fold increase in transcripts of one (Pi015853) encoding a homologue of a dynein light chain in Paramecium tetraurelia (CAK88700) (Judelson et al, 2009).…”

“…While the proteins in a number of zoospore secretory vesicles and flagellar surface components have been shown to be synthesized during sporangium formation (sporangiogenesis), the flagella themselves are assembled during sporangial cleavage (zoosporogenesis) from two basal bodies that lie adjacent to the pointed end of the pearshaped nuclei (Cope and Hardham, 1994;Hardham and Hyde, 1997). Studies of the transcriptomes of Phytophthora infestans, the cause of late blight of potato, have shown that the expression of specific sets of genes occurs during sporangiogenesis or zoosporogenesis (Judelson et al, 2008(Judelson et al, , 2009 In our studies of the sporulation transcriptomes of two broad host-range Phytophthora species, namely Phytophthora cinnamomi and Phytophthora nicotianae, we identified a gene that showed strong homology to the 22 kDa dynein light chain 1 (DLC1) protein of Chlamydomonas reinhardtii, LC1 . In C. reinhardtii, LC1 is one of 13 proteins that comprise the large (2 MDa) dynein outer arm attached to the A-tubule of the outer doublet microtubules of the flagellar axoneme (King, 2003;Pfister and Witman, 1982).…”

Genes found in partial sequencing of Phytophthora cinnamomi genome

“…They include more than 60 species of the genus Phytophthora. The best kwon potato late blight disease, which is caused by the fungus P. infestans, results in considerable loss of potato crop yield worldwide (Judelson et al, 2009). P. cinnamomi, a destructive and widespread soil-borne pathogen that infects woody plant hosts, has been estimated to directly affect over 2000 of the 9000 native plant species in the south west of Western Australia.…”