Colonization of Barley by the Broad-Host Hemibiotrophic Pathogen Phytophthora palmivora Uncovers a Leaf Development–Dependent Involvement of Mlo

Abstract

The discovery of barley Mlo demonstrated that filamentous pathogens rely on plant genes to achieve entry and lifecycle completion in barley leaves. While having a dramatic effect on foliar pathogens, it is unclear whether overlapping or distinct mechanisms affect filamentous pathogen infection of roots. To remove the bias connected with using different pathogens to understand colonization mechanisms in different tissues, we have utilized the aggressive hemibiotrophic oomycete pathogen Phytophthora palmivora. P. palmivora colonizes root as well as leaf tissues of barley (Hordeum vulgare). The infection is characterized by a transient biotrophy phase with formation of haustoria. Barley accessions varied in degree of susceptibility, with some accessions fully resistant to leaf infection. Notably, there was no overall correlation between degree of susceptibility in roots compared with leaves, suggesting that variation in different genes influences host susceptibility above and below ground. In addition, a developmental gradient influenced infection, with more extensive colonization observed in mature leaf sectors. The mlo5 mutation attenuates P. palmivora infection but only in young leaf tissues. The barley-P. palmivora interaction represents a simple system to identify and compare genetic components governing quantitative colonization in diverse barley tissue types.

A fungal ribonuclease-like effector protein inhibits plant host ribosomal RNA degradation

“…Similar patterns of susceptibility were also recently observed in barley leaves infected by P. palmivora (Le Fevre et al, 2016).…”

Time-resolved dual transcriptomics reveal early induced Nicotiana benthamiana root genes and conserved infection-promoting Phytophthora palmivora effectors

“…Transgenic P. palmivora LILI strains expressing KDEL-YFP [9] and tdTomato [71] have been previously described. Phytophthora growth conditions and the production of zoospores have been described elsewhere [10]. …”

“…Phytophthora palmivora , a tropical relative of P. infestans originating from southeastern Asia [3] but now present worldwide due to international trade [4], causes root, bud and fruit rotting diseases in many important tropical crops such as papaya, cocoa, oil palm, black pepper, rubber, coconut, durian, mango, cassava and citrus [5–8]. In addition, P. palmivora infects the roots and leaves of several model plant species such as Medicago truncatula [9], Hordeum vulgare [10] and Arabidopsis thaliana [11]. Despite its economic impact and widespread distribution, nothing is known about the molecular basis underlying its ability to infect its host species and the root responses associated with an infection.…”

Time-resolved dual root-microbe transcriptomics reveals early induced Nicotiana benthamiana genes and conserved infection-promoting Phytophthora palmivora effectors

“…Phytophthora palmivora, a broad-host-range tropical relative of P. infestans originating from south-eastern Asia [3] but now present worldwide due to international trade [4] causes root, bud and fruit rotting diseases in many important tropical crops such as papaya, cocoa, oil palm, black pepper, rubber, coconut, durian, mango, cassava and citrus [5][6][7][8]. In addition, P. palmivora infects roots and leaves of several model plant species such as Medicago truncatula [9], Hordeum vulgare [10] and Arabidopsis thaliana [11]. Despite its economic impact and widespread distribution, nothing is known about the molecular basis underlying its ability to infect many unrelated host species and the root responses associated with an infection.…”