Effect of temperature on enzymatic and physiological factors related to chilling injury in carambola fruit (Averrhoa carambola L.)

Three groups of carambola fruits (Averrhoa carambola L.) were stored at 2 and 10 degrees C (85-90% relative humidity). The major physicochemical, physiological, and enzymatic responses of fruit were measured in each group over a 30-day period: chilling injury index (CII), decay (%), intracuticular waxes, cuticle permeability, pulp firmness, weight loss, sucrose, fructose and glucose contents, ion electrolyte leakage in pulp (%), ethylene and carbon dioxide production rates, and the activities of peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzymes. CII values were statistically different at 2 and 10 degrees C, showing high significance with respect to sucrose content and weight loss (P < 0.05). Chilling injury included darkened ribs and skin desiccation. According to the CI symptom development, a possible relationship of POD and PPO activities was found at 2 degrees C. A significant sucrose content increase was observed at 10 degrees C. CI symptoms were associated with POD and PAL activities.     

Effect of pectic oligomers on physiological responses of chilling injury in discs excised from zucchini (Cucurbita pepo L.).

The effect of pectic oligomers (OG) on ethylene biosynthesis, electrolyte leakage (EL), and CO(2) production was studied in discs excised from zucchini fruit (Cucurbita pepo L.) and stored at 20 or 2.5 degrees C. At 20 degrees C, OG enhanced ethylene biosynthesis and had a transient effect on decreasing EL, but showed little effect on respiratory rate; both the amount and size of the oligomer were important in changing both ethylene synthesis and EL. At 2.5 degrees C, OG increased both ethylene biosynthesis and respiratory rate with a maximum effect at 100 microg of oligomer and peaking at 6 h; shorter oligomers demonstrated an even greater effect on ethylene biosynthesis, but differences were smaller in respiratory rate. EL at 2.5 degrees C was affected most by 1 microg of OG and by monomeric galacturonic acid, with transient increases that peaked at 8 h. We suggest a signaling role for OG in the early steps of cold acclimation or chilling injury.     

Secretome derived from breast tumor cell lines alters the morphology of human umbilical vein endothelial cells

Metastases, responsible for most of the solid tumor associated deaths, require angiogenesis and changes in endothelial cells. In this work, the effect of the secretomes of three breast tumor cell lines (MCF-7, MDA-MB-231 and ZR-75-30) on human umbilical vein endothelial cells (HUVEC) morphology was investigated. HUVEC treated with secretomes from breast cells were analyzed by confocal and time-lapse microscopy. Secretomes from ZR-75-30 and MDA-MB-231 cells modify the morphology and adhesion of HUVEC. These changes may provoke the loss of endothelial monolayer integrity. In consequence, tumor cells could have an increased access to circulation, which would then enhance metastasis.     

Microtubule plus end‐tracking proteins play critical roles in directional growth of hyphae by regulating the dynamics of cytoplasmic microtubules in Aspergillus nidulans

Cytoplasmic microtubules (MTs) serve as a rate‐limiting factor for hyphal tip growth in the filamentous fungus Aspergillus nidulans. We hypothesized that this function depended on the MT plus end‐tracking proteins (+TIPs) including the EB1 family protein EBA that decorated the MT plus ends undergoing polymerization. The ebAΔ mutation reduced colony growth and the mutant hyphae appeared in an undulating pattern instead of exhibiting unidirectional growth in the control. These phenotypes were enhanced by a mutation in another +TIP gene clipA. EBA was required for plus end‐tracking of CLIPA, the Kinesin‐7 motor KipA, and the XMAP215 homologue AlpA. In addition, cytoplasmic dynein also depended on EBA to track on most polymerizing MT plus ends, but not for its conspicuous appearance at the MT ends near the hyphal apex. The loss of EBA reduced the number of cytoplasmic MTs and prolonged dwelling times for MTs after reaching the hyphal apex. Finally, we found that colonies were formed in the absence of EBA, CLIPA, and NUDA together, suggesting that they were dispensable for fundamental functions of MTs. This study provided a comprehensive delineation of the relationship among different +TIPs and their contributions to MT dynamics and unidirectional hyphal expansion in filamentous fungi.     

Probiotics in the intestinal tract of juvenile whiteleg shrimp Litopenaeus vannamei: modulation of the bacterial community

Molecular analysis of the 16S rDNA of the intestinal microbiota of whiteleg shrimp Litopenaeus vannamei was examined to investigate the effect of a Bacillus mix (Bacillus endophyticus YC3-b, Bacillus endophyticus C2-2, Bacillus tequilensisYC5-2) and the commercial probiotic (Alibio^®) on intestinal bacterial communities and resistance to Vibrio infection. PCR and single strain conformation polymorphism (SSCP) analyses were then performed on DNA extracted directly from guts. Injection of shrimp with V. parahaemolyticus at 2.5 × 10⁵ CFU g^?1 per shrimp followed 168 h after inoculation with Bacillus mix or the Alibio probiotic or the positive control. Diversity analyses showed that the bacterial community resulting from the Bacillus mix had the highest diversity and evenness and the bacterial community of the control had the lowest diversity. The bacterial community treated with probiotics mainly consisted of α- and γ-proteobacteria, fusobacteria, sphingobacteria, and flavobacteria, while the control mainly consisted of α-proteobacteria and flavobacteria. Differences were grouped using principal component analyses of PCR-SSCP of the microbiota, according to the time of inoculation. In Vibrio parahaemolyticus-infected shrimp, the Bacillus mix (~33 %) induced a significant increase in survival compared to Alibio (~21 %) and the control (~9 %). We conclude that administration of the Bacillus mix induced modulation of the intestinal microbiota of L. vannamei and increased its resistance to V. parahaemolyticus.     

Irreversibility of chilling injury in zucchini squash (Cucurbita pepo L) could be a programmed event long before the visible symptoms are evident

Zucchini fruits were subjected to 2.5 or 10 degrees C for 16d, followed by transfer to 20 degrees C for 24h in order to evaluate the relationship between ripening pattern, measured as CO(2) evolution and ethylene (C(2)H(4)) production, and metabolic heat production (q). Chilling injury (CI) visible symptoms were evident after 8d at 2.5 degrees C, but none were recorded on fruits kept at 10 degrees C. In fruits held at 10 degrees C, q, C(2)H(4) production, and CO(2) evolution diminished in the course of 16d, whereas in those at 2.5 degrees C CO(2) evolution showed an early burst peaking at 8d. Both C(2)H(4) production and q also showed a burst at 2.5 degrees C but they started at 4 and 8d, respectively, and peaked at 12d. The results showed that irreversibility of chilling injury in zucchini could occur long before the appearance of visible symptoms, although the metabolic activity accompanying the irreversibility process was not noticeable by isothermal calorimetry.