Gr and hp-1 tomato mutants unveil unprecedented interactions between arbuscular mycorrhizal symbiosis and fruit ripening

Abstract

Main conclusion Systemic responses to an arbuscular mycorrhizal fungus reveal opposite phenological patterns in two tomato ripening mutants depending whether ethylene or light reception is involved. The availability of tomato ripening mutants has revealed many aspects of the genetics behind fleshy fruit ripening, plant hormones and light signal reception. Since previous analyses revealed that arbuscular mycorrhizal symbiosis influences tomato berry ripening, we wanted to test the hypothesis that an interplay might occur between root symbiosis and fruit ripening. With this aim, we screened seven tomato mutants affected in the ripening process for their responsiveness to the arbuscular mycorrhizal fungus Funneliformis mosseae. Following their phenological responses we selected two mutants for a deeper analysis: Green ripe (Gr), deficient in fruit ethylene perception and high-pigment-1 (hp-1), displaying enhanced light signal perception throughout the plant. We investigated the putative interactions between ripening processes, mycorrhizal establishment and systemic effects using biochemical and gene expression tools. Our experiments showed that both mutants, notwithstanding a normal mycorrhizal phenotype at root level, exhibit altered arbuscule functionality. Furthermore, in contrast to wild type, mycorrhization did not lead to a higher phosphate concentration in berries of both mutants. These results suggest that the mutations considered interfere with arbuscular mycorrhiza inducing systemic changes in plant phenology and fruits metabolism. We hypothesize a cross talk mechanism between AM and ripening processes that involves genes related to ethylene and light signaling.

Native soils with their microbiotas elicit a state of alert in tomato plants

“…'Battito' and 'Cuore di Bue' are resistant and susceptible, respectively, to FOL races 1 and 2, as stated by the producer and verified in a previous study (Poli et al, 2016). To remove the seed microbiota (Shade et al, 2017), in all experiments seeds were disinfected as detailed in Chialva et al (2016), at least removing the seed ectosphere. Soils used were the same as those used by Poli et al (2016).…”

“…To remove the seed microbiota (Shade et al ., ), in all experiments seeds were disinfected as detailed in Chialva et al . (), at least removing the seed ectosphere. Soils used were the same as those used by Poli et al .…”

“…RNA was isolated using the modified 'pine-tree method' as described earlier. Material was quality-checked, processed to remove DNA, and retrotranscribed as described in Chialva et al (2016). RT-qPCR amplifications and data analysis were performed as described in Methods S3.…”

Rhizosphere-enriched microbes as a pool to design synthetic communities for reproducible beneficial outputs

“…Tomato ( Solanum lycopersicum ) cv. Ailsa Craig seeds were surface-sterilized 45 and sown into 10.5 cm diameter pots, each containing 200 gr sterilized peat-based potting substrate (Plantobalt substrate 2, Plantaflor) 26 , alone or with a SynCom. Plants were grown in a controlled growth chamber (25°C; 16h light, 8h dark; 65–70% RH; light intensity 450 μmol m −2 s −1 at pot height) and received watering individually every second day with equal volume of water.…”

Physiological Beneficial Effect of Rhizophagus intraradices Inoculation on Tomato Plant Yield under Water Deficit Conditions

“…Beneficial effects of AM symbiosis on tomato plants are reported in literature [15,27]. In addition, to the expected effects on roots [48,51,52], AMF colonization contributes to modify gene expression in tomato fruits [53,54] and leaves, in particular genes involved in defense process, transport and hormonal metabolisms [55,56] as well as in lignin synthesis [15]. As previously mentioned, the beneficial effects of AM symbiosis observed during this experiment are the basis of an economic feasibility study aiming at the promotion of production and commercialization of mycorrhizal tomato plantlets.…”