The Rare Sugar Tagatose Differentially Inhibits the Growth of Phytophthora infestans and Phytophthora cinnamomi by Interfering With Mitochondrial Processes

The Differential Growth Inhibition of Phytophthora spp. Caused by the Rare Sugar Tagatose Is Associated With Species-Specific Metabolic and Transcriptional Changes

“…Likewise, genes implicated in the tricarboxylic acid (TCA) cycle (e.g., malate synthase, succinate-semialdehyde dehydrogenase, succinate dehydrogenase and pyruvate dehydrogenase) and mitochondrial respiration (e.g., ubiquinone biosynthesis protein COQ7, cytochrome b5 and, NADH dehydrogenase), were down-and up-regulated by tagatose incubation in P. infestans and P. cinnamomi, respectively. In agreement with these findings, tagatose incubation decreased the content of TCA cycle intermediates in P. infestans (such as malic acid and succinic acid) (Corneo et al, 2021) and impaired normal respiration and ATP synthesis in P. infestans, but not in P. cinnamomi (Chahed et al, 2020), indicating species-specific effects of tagatose on some pathways of energy metabolism. As a possible consequence of energy limitation, genes associated with growth and development (e.g., myosin-like protein and actin-like protein) were mainly down-and up-regulated by tagatose incubation in P. infestans and P. cinnamomi, respectively.…”

“…Phytophthora infestans strain VB3 and P. cinnamomi strain CBS 144.22 were stored in glycerol at −80 • C in the fungal collection of the Fondazione Edmund Mach and they are available upon request. P. infestans and P. cinnamomi were grown in Petri dishes on pea agar medium (PAM; 12.5% frozen peas and 1.2% agar in distilled water) at 18 and 25 • C in dark conditions, respectively (Chahed et al, 2020). The stock solution (50 g/L in distilled water) of tagatose (Bi-PA, Londerzeel, Belgium) was filter sterilized and added at the final concentration of 5 g/L on PAM shortly before Phytophthora spp.…”

“…For metabolic and transcriptomic analyses, a plug (5 mm diameter and 2 mm height) of a 14 days-old colony was placed on PAM covered with sterile cellophane layers in the absence (control) and presence of 5 g/L tagatose. P. infestans and P. cinnamomi samples were collected at 4 and at 10 DAI after incubation at 18 and 25 • C, respectively, as previously described (Chahed et al, 2020). Briefly, mycelium samples were collected with a sterile forceps, transferred in a sterile 50 mLtube, immediately frozen in liquid nitrogen and stored at −80 • C. Samples were crushed using a mixer mill disruptor (MM200, Retsch, Haan, Germany) at 25 Hz for 45 s with sterile steel jars and beads refrigerated in liquid nitrogen.…”

“…The first strand cDNA was synthesized from 1 µg of DNase-treated RNA using Superscript III (Invitrogen, Thermo Fisher Scientific) and the oligo-dT primer. qPCR reactions were carried out with Platinum SYBR Green qPCR SuperMix-UDG (Invitrogen, Thermo Fisher Scientific) and specific primers using the Light Cycler 480 (Roche Diagnostics, Mannheim, Germany), as previously described (Chahed et al, 2020). Briefly, the PCR conditions were: 50 • C for 2 min and 95 • C for 2 min as initial steps, followed by 50 cycles of 95 • C for 15 s and 60 • C for 1 min.…”

“…Tagatose inhibited the growth of several causal agents of plant diseases, such as Phytophthora infestans (tomato and potato late blight) ( Chahed et al, 2020 ), Plasmopara viticola (grapevine downy mildew) and Erysiphe necator (grapevine powdery mildew) ( Perazzolli et al, 2020 ), Hyaloperonospora parasitica (cabbage downy mildew) and Oidium violae (tomato powdery mildew) ( Mochizuki et al, 2020 ; Mijailovic et al, 2021 ). Tagatose showed also possible prebiotic effects on the phyllosphere microbiota and shifted the proportions of potential beneficial and potential pathogenic microorganisms by a selective nutritional or anti-nutritional effect on plant-associated microorganisms ( Perazzolli et al, 2020 ).…”