Xanthomonas oryzae pv. exoribonuclease R is required for complete virulence in rice, optimal motility, and growth under stress

Exoribonuclease R (RNase R) is a 3’ hydrolytic exoribonuclease that can degrade structured RNA. Mutation in RNase R affects virulence of certain human pathogenic bacteria. The aim of this study was to determine whether RNase R is required for virulence of the phytopathogen that causes bacterial blight in rice, Xanthomonas oryzae pv. oryzae (Xoo). In silico analysis has indicated that RNase R is highly conserved among various Xanthomonads. Amino acid sequence alignment of Xoo RNase R with RNase R from various taxa indicated that Xoo RNase R clustered with RNase R of order Xanthomonadales. In order to study its role in virulence, a gene disruption mutant of Xoo RNase R (rnr –) was generated. The Xoo rnr – mutant is moderately virulence deficient and the complementing strain (rnr –/pHM1::rnr) rescued the virulence deficiency of the mutant. We investigated swimming and swarming motilities in both nutrient deficient minimal and nutrient optimal media. We observed that rnr – mutant has adversely affected the swimming and swarming motilities of Xoo in optimal media. However, in nutrient deficient media only swimming motility was noticeably affected. Growth curves in optimal media at suboptimal temperature (15°C, cold stress) indicate that Xoo rnr – mutant grows slower than Xoo wild type (wt) and complementing strain (rnr –/pHM1::rnr). Taken together, we report for the first time that RNase R function is necessary for complete virulence of Xoo in rice. It is also important for motility of Xoo in media and for growth of Xoo at suboptimal temperature.

Efectul șocului termic a temperaturilor suboptimale pozitive și a preparatului Reglalg asupra indicilor germinativi ai semințelor de castravete Cucumis Sativus L

Cucumber (Cucumis sativus L.), cv Concurent and forms as Plai, F1; ELITA, F1; ASSIA, F1; Viorel, F1 și Cernomor, F1 seeds treated with distillate water (control) or water solutions of Reglalg preparation (1/100 and 1/1000 dilutions) were germinated at 27°C (control) or at different sub optimal positive low temperature (15°C, 13°C, 10°C, 8°C, 6°C and 4°C) to study germination characteristics. Final germination percent of cv Concurent seeds and germination energy decreased, while the conditional number of days, required for germination of one seed, increased with the decrease of temperature. The temperature of 13°C is the minimum below which all cucumber seeds do not germinate. Application of Reglalg preparation (dilution 1/1000) had a beneficial effect on the germination parameters under suboptimal temperature of 15⁰C.

Acid fish silage in the diet of pacu and tambacu reared at cold suboptimal temperature

The objective of this work was to evaluate the supplementation of diet of pacu and tambacu with acid fish silage during winter. The experimental design was a 2 × 2 factorial arrangement (two genetic groups and two diets), with three replicates. The genetic group factor was composed of pacu (Piaractus mesopotamicus) and tambacu (♀ Colossoma macropomum × ♂ Piaractus mesopotamicus). The two diets were based on plant ingredients; one of them was supplemented with acid fish silage (silage diet), and the other was a base diet without supplementation. Twelve net tanks, six from which with pacu, and six with tambacu, were used as experimental units, with ten fish in each tank. There was an interaction of the factors for final length, final weight, and daily weight gain. Pacu fed the silage diet showed a higher growth than pacu fed with the base diet; however, this effect was not observed for tambacu. A higher feed efficiency was observed for pacu than for tambacu, without a diet effect. The diet supplementation with acid fish silage improves the productive performance of pacu reared at cold suboptimal temperature, but it does not have this effect on tambacu.