Evaluation of aluminium tolerance in grapevine rootstocks

Aluminum (Al) toxicity is a major worldwide agricultural problem. At low pH, Al speciates into the soluble and phyto-toxic form Al3+, inhibiting the root growth and affecting plant development. In Brazil, agriculture in acidic soils with elevated concentration of Al has significantly increased in the last decades. Therefore, in order to achieve efficient agriculture practices, the selection of plant cultivars with improved Al resistance has become crucial in this type of soils. In this work we have evaluated the Al resistance of six genotypes of grapevine rootstocks. The grapevine hardwood cuttings were grown in nutrient solution in the absence and presence of 250 and 500 μM Al at pH 4.2. The phenotypic indexes of relative root growth, fresh and dry root weight, root area, hematoxylin staining profile, and Al content were evaluated for all six genotypes. These phenotypic indexes allowed us to identify the 'Kober 5BB', 'Gravesac', 'Paulsen 1103', and 'IAC 766' grapevine rootstocks genotypes as the ones with the highest resistance to Al. Likewise, 'IAC 572' and 'R110 genotypes were the most Al-sensitive cultivars. We evaluated the root organic acid exudation profile in the most Al-resistant ('Kober 5BB') and most Al-sensitive ('R110') in plantlets cultivated in vitro in the absence and presence of 100, 200, and 400 μM of Al. Among several compounds detected, citrate was the only organic acid related to the Al resistance phenotype observed in the 'Kober 5BB' genotype. The high constitutive citrate exudation observed in 'Kober 5BB' strongly suggests that exudation of this particular organic acid may impart Al-resistance/amelioration in grapevine.

Multifaceted roles of nitric oxide in tomato fruit ripening: NO-induced metabolic rewiring and consequences for fruit quality traits

Nitric oxide (NO) has been implicated as part of the ripening regulatory network in fleshy fruits. However, very little is known about the simultaneous action of NO on the network of regulatory events and metabolic reactions behind ripening-related changes in fruit color, taste, aroma and nutritional value. Here, we performed an in-depth characterization of the concomitant changes in tomato (Solanum lycopersicum) fruit transcriptome and metabolome associated with the delayed-ripening phenotype caused by NO supplementation at the pre-climacteric stage. Approximately one-third of the fruit transcriptome was altered in response to NO, including a multilevel down-regulation of ripening regulatory genes, which in turn restricted the production and tissue sensitivity to ethylene. NO also repressed hydrogen peroxide-scavenging enzymes, intensifying nitro-oxidative stress and S-nitrosation and nitration events throughout ripening. Carotenoid, tocopherol, flavonoid and ascorbate biosynthesis were differentially affected by NO, resulting in overaccumulation of ascorbate (25%) and flavonoids (60%), and impaired lycopene production. In contrast, the biosynthesis of compounds related to tomato taste (sugars, organic acids, amino acids) and aroma (volatiles) was slightly affected by NO. Our findings indicate that NO triggers extensive transcriptional and metabolic rewiring at the early ripening stage, modifying tomato antioxidant composition with minimal impact on fruit taste and aroma.This work was supported by the São Paulo Research Foundation (FAPESP) (grants 2018/16389-8, 2016/04924-0, 2017/17935-3 and 2016/01128-9), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (grants 422287/2018-0, 305012/2018-5, 303332/2019-0 and 300986/2018-1), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. The research work of FJC and JMP is supported by a European Regional Development Fund cofinanced grant from the Ministry of Economy and Competitiveness (AGL2015-65104-P and PID2019-103924GB-I00), Spain

Carotenoid accumulation during tomato fruit ripening is modulated by the auxin-ethylene balance

Background : Tomato fruit ripening is controlled by ethylene and is characterized by a shift in color from green to red, a strong accumulation of lycopene, and a decrease in β-xanthophylls and chlorophylls. The role of other hormones, such as auxin, has been less studied. Auxin is retarding the fruit ripening. In tomato, there is no study of the carotenoid content and related transcript after treatment with auxin. Results : We followed the effects of application of various hormone-like substances to “Mature-Green” fruits. Application of an ethylene precursor (ACC) or of an auxin antagonist (PCIB) to tomato fruits accelerated the color shift, the accumulation of lycopene, α-, β-, and δ-carotenes and the disappearance of β-xanthophylls and chlorophyll b. By contrast, application of auxin (IAA) delayed the color shift, the lycopene accumulation and the decrease of chlorophyll a. Combined application of IAA + ACC led to an intermediate phenotype. The levels of transcripts coding for carotenoid biosynthesis enzymes, for the ripening regulator Rin, for chlorophyllase, and the levels of ethylene and abscisic acid (ABA) were monitored in the treated fruits. Correlation network analyses suggest that ABA, may also be a key regulator of several responses to auxin and ethylene treatments. Conclusions : The results suggest that IAA retards tomato ripening by affecting a set of (i) key regulators, such as Rin, ethylene and ABA, and (ii) key effectors, such as genes for lycopene and β-xanthophyll biosynthesis and for chlorophyll degradation

Proton and anion transport across the tonoplast vesicles in bromeliad species

Crassulacean acid metabolism (CAM) is one of the key innovations in the Neotropical family Bromeliaceae that has enabled many of its species to occupy seasonally water-limited terrestrial environments or microclimatically arid epiphytic niches. However, the relationship between CAM activity and the transport processes responsible for vacuolar organic-acid accumulation at night has not been systematically explored in this family. In the present investigation, ATP- and PPi-dependent proton transport rates were studied in tonoplast membrane vesicles isolated from leaves of six CAM and one C3 species of bromeliads. A consistent feature of these species was the high activity of the tonoplast ATP-driven H+ pump, which, when averaged across the seven species tested, showed a higher specific activity than the tonoplast PPi-driven H+ pump. For all CAM species, the rate of ATP-dependent proton transport into the tonoplast vesicles was strongly influenced by the nature of the balancing organic-acid anion, which displayed the following order of effectiveness: fumarate > malate > citrate. Measurements of leaf organic-acid content in six CAM bromeliads at dusk and dawn showed that nocturnal accumulation of malate exceeded citrate by a factor of ~2.4–20.0-fold in five of six bromeliad species used in this study, demonstrating a close correlation between the CAM rhythm and the intrinsic properties of the vacuolar membrane across which these organic acids are transported

Current challenges in postharvest biology of fruit ripening.

This paper reviews the recent advances in the understanding of the fruit ripening process and describes future challenges. Fruit ripening is a complex developmental process which is orchestrated by the expression of ripening-related genes under the control of a network of signaling pathways. In climacteric fruit components responsible for the production of climacteric ethylene have been identified. Less progress has been made on non-climacteric fruit. Great advances have been made in the characterization of transcription factors (ERFs, RIN, etc?) that induce gene expression through the binding to their promoters. Genetic resources, genome sequencing and ?omics? tools have been developed bringing a huge amount of data that will help to draw together an integrative network of regulatory and signaling pathways responsible for triggering and coordinating the ripening process. The discovery that some ripening events are controlled at the epigenetic level and, not in relation with the DNA sequences, opens novel perspectives

Methyl jasmonate as a tool to improve anthocyanins on grapes grown on subtropical climate

Vitis labrusca L. grapes are largely cultivated in Brazil, but the tropical climate affect negatively the phenols content, especially anthocyanins. In the future, due to the global climate changes, such phenomenon could expand in more regions. Therefore, many researches focus on increasing grape phenols content, and methyl jasmonate (MeJa) treatment could be a good alternative. Since studies on Vitis vinifera L. grapes gave promising results, the aim of this study was to evaluate anthocyanin changes caused by the MeJa pre-harvest application on two Vitis labrusca L. cultivars grape, both grown in two Brazilian regions. Isabel Precoce and Concord grapes cultivated under subtropical climate on south and southeast of Brazil, received MeJa pre-harvest treatment. Grape metabolites were extracted and analyzed with a MS based metabolomics protocol by UPLC-HRMS-QTOF. Unsupervised data analysis reveals clear separation between the two regions and the two cultivars, while supervised data analysis revealed biomarkers between MeJa and control group. Among the varieties, Concord grapes were more responsive to the treatment, while Isabel Precoce cultivated on the south was the least responsive one. We annotated 35 anthocyanins, such cyanidin, peonidin, delphinidin, malvidin and petunidin in the caffeoyl, acetyl and p-coumaroyl mono and diglucoside derivatives. We observed, that MeJa promoted higher amounts of anthocyanins 3’ hydroxylated, acetylated and coumarylated derivatives forms, with exception of Isabel Precoce grapes cultivated on southeast region. Our results suggested that MeJa could be used as elicitor to secondary metabolism in grapes grown even under subtropical climate, affecting anthocyanin biosynthesis

LC–MS untargeted approach showed that methyl jasmonate application on Vitis labrusca L. grapes increases phenolics at subtropical Brazilian regions

Introduction Vitis labrusca L. grapes are largely cultivated in Brazil, but the tropical climate negatively affects the phenols content, especially anthocyanin. According to the projections of the incoming climatic changes, the climate of several viticulture zone might change to tropical. Therefore, researches are focusing on increasing grape phenols content; with methyl jasmonate application (MeJa) is considered a good alternative. Objectives The aim was to investigate with an untargeted approach the metabolic changes caused by the MeJa pre-harvest application on two Vitis labrusca L. cultivars grapes, both of them grown in two Brazilian regions. Methods Isabel Precoce and Concord grapes cultivated under subtropical climate, in the south and southeast of Brazil, received MeJa pre-harvest treatment. Grape metabolome was extracted and analyzed with a MS based metabolomics protocol by UPLC-HRMS-QTOF. Results Unsupervised data analysis revealed a clear separation between the two regions and the two cultivars, while supervised data analysis revealed biomarkers between the MeJa treatment group and the control group. Among the metabolites positively affected by MeJa were (a) flavonoids with a high degree of methylation at the B-ring (malvidin and peonidin derivatives and isorhamentin) for Isabel Precoce grapes; (b) glucosides of hydroxycinnamates, gallocatechin, epigallocatechin and cis-piceid for Concord grapes; and (c) hydroxycinnamates esters with tartaric acid, and procyanidins for the Southeast region grapes. Conclusion These results suggest that MeJa can be used as elicitor to secondary metabolism in grapes grown even under subtropical climate, affecting phenolic biosynthesis