Willian Batista Silva

The chitosan affects severely the carbon metabolism in mango (Mangifera indica L. cv. Palmer) fruit during storage

Mango is a highly perishable fruit with a short post-harvest time due to the intense metabolic activity after harvesting. In attempt to evaluate the effects of chitosan in mango fruits, it was treated with 0%, 1%, 2% or 3% of chitosan solutions, placed into plastic trays, and stored at room temperature. Changes in physical and chemical parameters were evaluated. Chitosan delayed the climacteric peak, water loss and firmness. Further, few changes in soluble solid content, titratable acidity, pH of the pulp as well as in sugar content and decreased starch degradation were observed. Altogether, our results suggest chitosan edible coating effectively prolongs the quality attributes, affecting basic mitochondrial respiration and starch degradation rate.

Impaired Malate and Fumarate Accumulation Due to the Mutation of the Tonoplast Dicarboxylate Transporter Has Little Effects on Stomatal Behavior

Manipulation of tonoplastic organic acid transport by inhibition of the tDT impacts mitochondrion metabolism, while the overall stomatal and photosynthetic performance is not affected. Malate is a central metabolite involved in a multiplicity of plant metabolic pathways, being associated with mitochondrial metabolism and playing significant roles in stomatal movements. Vacuolar malate transport has been characterized at the molecular level and is performed by at least one carrier protein and two channels in Arabidopsis (Arabidopsis thaliana) vacuoles. The absence of the Arabidopsis tonoplast Dicarboxylate Transporter (tDT) in the tdt knockout mutant was associated previously with an impaired accumulation of malate and fumarate in leaves. Here, we investigated the consequences of this lower accumulation on stomatal behavior and photosynthetic capacity as well as its putative metabolic impacts. Neither the stomatal conductance nor the kinetic responses to dark, light, or high CO2 were highly affected in tdt plants. In addition, we did not observe any impact on stomatal aperture following incubation with abscisic acid, malate, or citrate. Furthermore, an effect on photosynthetic capacity was not observed in the mutant lines. However, leaf mitochondrial metabolism was affected in the tdt plants. Levels of the intermediates of the tricarboxylic acid cycle were altered, and increases in both light and dark respiration were observed. We conclude that manipulation of the tonoplastic organic acid transporter impacted mitochondrial metabolism, while the overall stomatal and photosynthetic capacity were unaffected.

Chitosan delays ripening and ROS production in guava (Psidium guajava L.) fruit

Guava is a typically tropical fruit highly perishable with a short shelf-life due to intense metabolic activity after harvested. In attempt to minimize the problems related to the postharvest, we evaluated the physiochemical characteristics and antioxidant system in guava fruits under chitosan coating at concentrations of 1%, 2%, and 3% stored at 25°C during 96h. The chitosan suppressed the respiratory rate, fresh weight loss, firmness and skin color with delay in the degradation of chlorophyll. In the treatment with 2% and 3% of chitosan in the solid soluble content and ascorbic acid were reduced; retarded the loss of titratable acidity during 96h after treatment. These treatment induced significant decreases in the phenylalanine ammonia-lyase activity and significantly increases of peroxidase Activity. Our results suggest that chitosan effectively prolongs the quality attributes in guava fruits after harvesting due to increases in the antioxidant processes, delaying the ripening during room temperature of storage.

SELF-PRUNING Acts Synergistically with DIAGEOTROPICA to Guide Auxin Responses and Proper Growth Form

The antiflorigenic signal SELF-PRUNING controls tomato growth habit by affecting auxin transport, signaling, and metabolism. The SELF PRUNING (SP) gene is a key regulator of growth habit in tomato (Solanum lycopersicum). It is an ortholog of TERMINAL FLOWER1, a phosphatidylethanolamine-binding protein with antiflorigenic activity in Arabidopsis (Arabidopsis thaliana). A spontaneous loss-of-function mutation (sp) has been bred into several industrial tomato cultivars, as it produces a suite of pleiotropic effects that are favorable for mechanical harvesting, including determinate growth habit, short plant stature, and simultaneous fruit ripening. However, the physiological basis for these phenotypic differences has not been thoroughly explained. Here, we show that the sp mutation alters polar auxin transport as well as auxin responses, such as gravitropic curvature and elongation of excised hypocotyl segments. We also demonstrate that free auxin levels and auxin-regulated gene expression patterns are altered in sp mutants. Furthermore, diageotropica, a mutation in a gene encoding a cyclophilin A protein, appears to confer epistatic effects with sp. Our results indicate that SP affects the tomato growth habit at least in part by influencing auxin transport and responsiveness. These findings suggest potential novel targets that could be manipulated for controlling plant growth habit and improving productivity.

ATIVIDADE RESPIRATÓRIA EM MITOCÔNDRIAS ISOLADAS DA POLPA DO MAMÃO UENF/CALIMAN 01 E TAINUNG 01 NA CONSERVAÇÃO DO FRUTO EM PÓS-COLHEITA

This study had the object of comparing the respiratory activity in isolated mitochondria and the physical and chemical attributes of the pulp of two papaya hybrids, UENF/Caliman01 and Tainung01, during fruit ripening. The fruit ripening did not show significant differences between the genotypes with regard to lightness (L), chroma (C), and hue angle of the skin. The loss of mass (LM) and the firmness of fruit (FF) and mesocarp (FM) differed between the genotypes, with FF and FM decreasing with time after harvest, while LM rose over the same period. The respiratory activity in the isolated mitochondria revealed differences between the genotypes with respect to total respiration (TR), being higher and with negative time-correlation function in Tainung01 and constant in UC01 during fruit ripening. During this period the participation of alternative oxidase (AOX) pathway was crescent, against the decreasing participation of cytochrome c oxidase (COX) pathway in both hybrids was verified, indicating an increasing uncoupling of the mitochondria, which may be associated with the rapid biochemical transformations that cause the senescence of the organ. From these results, investigating genetic materials with lower AOX activity or ways of minimizing the respiratory activity in postharvest fruit is suggested. The AOX presented the high positive correlation with LM and negative with FF and FM while the inverse was observed for COX. The TR presented positive correlation only with the FM. The correlations indicated the viability of estimated respiratory activity through simpler analyses such as LM, FF, and FM, thus facilitating studies in the area.

TRATAMENTO COM CLORETO DE CÁLCIO NA PÓS-COLHEITA RETARDA O DESVERDECIMENTO E A PERDA DE FIRMEZA DO MAMÃO UENF/CALIMAN01

In order to prolong the shelf life and maintain the quality of Papaya/UENF/Caliman01, different concentrations of CaCl2 applied by vacuum infiltration were tested. The fruit were separated into six groups: control (no treatment) and treatments with CaCl2 at 0%, 2%, 4%, 6%, and 8% CaCl2 (w/v), applied by immersion under vacuum during 3 min at 50kPa tension. Further analysis was then performed with respect to weight loss, fruit firmness, mesocarp firmness, hue angle color, soluble solids (SS), titratable acidity (TA), ascorbic acid, total sugars, and the SS/TA ratio. The calcium treatment did not affect the weight loss, which generally increased over time. However, the fruit remained green and firm longer when treated with CaCl2 at 6% and 8% (w/v). The use of CaCl2 did not affect chemical fruit characteristics such as soluble solids, titratable acidity, and SS/TA ratio, but did decrease the synthesis of ascorbic acid and the degradation of soluble sugars.

SELF-PRUNING affects auxin responses synergistically with the cyclophilin A DIAGEOTROPICA in tomato

Summary The antiflorigenic signal SELF-PRUNING, which controls growth habit, exerts its effects through auxin transport, signaling and metabolism in tomato. Abstract The SELF PRUNING (SP) gene is a key regulator of growth habit in tomato (Solanum lycopersicum). It is an ortholog of TERMINAL FLOWER 1, a phosphatidyl-ethanolamine binding protein with anti-florigenic activity in Arabidopsis thaliana. A spontaneous loss-of-function sp mutation has been bred into a large number of industrial tomato cultivars, as it produces a suite of pleiotropic effects that are favorable for mechanical harvesting, including determinate growth habit, short plant stature and simultaneous fruit ripening. However, the physiological basis for these phenotypic differences has not been thoroughly explained. Here, we show that the sp mutation alters polar auxin transport as well as auxin responses such gravitropic curvature and elongation of excised hypocotyl segments. We further demonstrate that free auxin levels and auxin-regulated gene expression patterns are altered in sp, with epistatic effects of diageotropica, a mutation in a cyclophilin A protein-encoding gene. Our results indicate that SP impacts growth habit in tomato, at least in part, via changes in auxin transport and responsiveness. These findings hint at novel targets that could be manipulated in the control of growth habit and productivity.

How Does European Mistletoe Survive Without Complex I

Two independent but complementary studies recently provided the first biochemical proof of the complete absence of mitochondrial Complex I in a multicellular eukaryote. The mitochondrial electron transport chain (mETC) of the hemiparasitic European mistletoe (Viscum album) displays dramatic rearrangements of its components, most likely reflecting its parasitic lifestyle.