Molecular analysis of the early interaction between the grapevine flower and Botrytis cinerea reveals that prompt activation of specific host pathways leads to fungus quiescence

Abstract

Grape quality and yield can be impaired by bunch rot, caused by the necrotrophic fungus Botrytis cinerea. Infection often occurs at flowering, and the pathogen stays quiescent until fruit maturity. Here, we report a molecular analysis of the early interaction between B. cinerea and Vitis vinifera flowers, using a controlled infection system, confocal microscopy and integrated transcriptomic and metabolic analysis of the host and the pathogen. Flowers from fruiting cuttings of the cultivar Pinot Noir were infected with green fluorescent protein (GFP)-labelled B. cinerea and studied at 24 and 96 hours post-inoculation (h.p.i.). We observed that penetration of the epidermis by B. cinerea coincided with increased expression of genes encoding cell-wall-degrading enzymes, phytotoxins and proteases. Grapevine responded with a rapid defence reaction involving 1193 genes associated with the accumulation of antimicrobial proteins, polyphenols, reactive oxygen species and cell wall reinforcement. At 96 h.p.i., the reaction appears largely diminished both in the host and in the pathogen. Our data indicate that the defence responses of the grapevine flower collectively are able to restrict invasive fungal growth into the underlying tissues, thereby forcing the fungus to enter quiescence until the conditions become more favourable to resume pathogenic development.

Neofusicoccum parvum Colonization of the Grapevine Woody Stem Triggers Asynchronous Host Responses at the Site of Infection and in the Leaves

“…The TCP (TEOSINTE BRANCHED 1, CYCLOIDEA, and PCF1), HSF (heat stress factor), LIM, and bromodomain TF family genes were found among leaf hubs. Interestingly, the hubs of the leaf “turquoise” module included VvWRKY33 ( VIT_06s0004g07500 ), which was previously shown to be induced in grape leaves by both downy mildew and dehydration stress (Merz et al, 2015; Hopper et al, 2016), as well as in grape flowers by Botrytis cinerea (Haile et al, 2017). …”

Dual Transcriptome and Metabolic Analysis of Vitis vinifera cv. Pinot Noir Berry and Botrytis cinerea During Quiescence and Egressed Infection

“…A genetically transformed B. cinerea strain, B05.10, expressing a green fluorescent protein (GFP) was used as in Haile et al, 2017. Grapevine fruiting cuttings obtained from Pinot Noir winter woody cuttings were grown and infected as described in Haile et al, 2017. Flowers at full cap-fall stage [EL25/26, according to Eichorn and Lorenz (1977)] were inoculated by placing a 1.5 µl droplet of either conidia solution of GFP-labeled B05.10 (2*10 5 ml -1 ) or distilled water (mock inoculation) close to the receptacle area. Conidia were obtained from B. cinerea grown on PDA at 25°C for 10 days, and the concentration was determined using a hemacytometer under light microscope.…”

Expression of disease resistance in genetically modified grapevines correlates with the contents of viral sequences in the T-DNA and global genome methylation

“…Grapevine responses to B. cinerea initially employ structural defense mechanisms, consisting of preexistent physical barriers, such as cuticle and trichomes (Wan et al 2015). The initial responses are coupled with inducible pathways, leading to strengthening of the plant cell wall, secretion fungus cell wall degrading enzymes, and production of proteins involved in oxidative burst, or with antimicrobial properties (Haile et al 2017). These responses were shown to restrict the growth of the invasive hyphae into the underlying plant tissues, which leads the pathogen to remain quiescent until favorable conditions occur and allow the evolution of pathogenesis (Haile et al 2017).…”

“…The initial responses are coupled with inducible pathways, leading to strengthening of the plant cell wall, secretion fungus cell wall degrading enzymes, and production of proteins involved in oxidative burst, or with antimicrobial properties (Haile et al 2017). These responses were shown to restrict the growth of the invasive hyphae into the underlying plant tissues, which leads the pathogen to remain quiescent until favorable conditions occur and allow the evolution of pathogenesis (Haile et al 2017). Changes in the plant developmental programs and cellular signals are hypothesized to trigger pathogen egression resuming the pathogenic process (Haile et al 2017).…”

“…These responses were shown to restrict the growth of the invasive hyphae into the underlying plant tissues, which leads the pathogen to remain quiescent until favorable conditions occur and allow the evolution of pathogenesis (Haile et al 2017). Changes in the plant developmental programs and cellular signals are hypothesized to trigger pathogen egression resuming the pathogenic process (Haile et al 2017). The proteins ectopically expressed in the current study are associated to the initial stages of infection, namely: hydrolysis of the cell wall in several fungal structures (chitinase, in CHIT lines) (Bogo et al 1998) and toxic effects to actively growing points (osmotin-like, in OLP lines) (Campos et al 2008;Chowdhury et al 2017).…”