Capsicum is the genus where a number of species and varieties have pungent features due to the exclusive content of capsaicinoids such as capsaicin and dihydrocapsaicin. In this work, the main enzymatic and non-enzymatic systems in pepper fruits from four varieties with different pungent capacity have been investigated at two ripening stages. Thus, a sweet pepper variety (Melchor) from California-type fruits and three autochthonous Spanish varieties which have different pungency levels were used, including Piquillo, Padrón and Alegría riojana. The capsaicinoids contents were determined in the pericarp and placenta from fruits, showing that these phenyl-propanoids were mainly localized in placenta. The activity profiles of catalase, total and isoenzymatic superoxide dismutase (SOD), the enzymes of the ascorbate–glutathione cycle (AGC) and four NADP-dehydrogenases indicate that some interaction with capsaicinoid metabolism seems to occur. Among the results obtained on enzymatic antioxidants, the role of Fe-SOD and the glutathione reductase from the AGC is highlighted. Additionally, it was found that ascorbate and glutathione contents were higher in those pepper fruits which displayed the greater contents of capsaicinoids. Taken together, all these data indicate that antioxidants may contribute to preserve capsaicinoids metabolism to maintain their functionality in a framework where NADPH is perhaps playing an essential role.

A gene coding for an aminoglycoside 6'-N-acetyltransferase that was able to modify amikacin was cloned from a plasmid isolated from a clinical strain of Enterobacter cloacae. Sequencing of a 955-bp segment which mediates the modifying activity revealed a single open reading frame of 432 nucleotides that predicted a polypeptide of 144 amino acid residues with a molecular weight of 16,021. Putative ribosomal binding sites and -10 and -35 sequences were located at the 5' end of the gene. The size of the polypeptide was confirmed through minicell analysis of the expression products of plasmids containing the sequence. The use of the gene as a molecular probe revealed its specificity toward strains harboring genes coding for related enzymes. This probe is therefore useful for epidemiological studies.

Key message The activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion. Therefore, rootstock selection is key to improve crop performance and a sustainable production under changing climate conditions. Abstract Climate change is altering weather conditions such as mean temperatures and precipitation patterns. Rising temperatures, especially in certain regions, accelerates soil water depletion and increases drought risk, which affects agriculture yield. Previously, our research demonstrated that the citrus rootstock Carrizo citrange (Citrus sinensis × Poncirus trifoliata) is more tolerant than Cleopatra mandarin (C. reshni) to drought and heat stress combination, in part, due to a higher activation of the antioxidant system that alleviated damage produced by oxidative stress. Here, by using reciprocal grafts of both genotypes, we studied the importance of the rootstock on scion performance and antioxidant response under this stress combination. Carrizo rootstock, under stress combination, positively influenced Cleopatra scion by reducing H2O2 accumulation, increasing superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymatic activities and inducing SOD1, APX2 and catalase (CAT) protein accumulations. On the contrary, Cleopatra rootstock induced decreases in APX2 expression, CAT activity and SOD1, APX2 and CAT contents on Carrizo scion. Taken together, our findings indicate that the activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion and highlight the importance of the rootstock selection to improve crop performance and maintain citrus yield under the current scenario of climate change.

Two genes encoding for aminoglycoside-(3)-N-acetyltransferases (AAC(3)s) of different substrate patterns, present in multiresistance plasmids of hospital strains of Serratia marcescens and Escherichia coli isolated from urine, have been cloned and characterized. The first, aacC1 with AAC(3)I activity, contained a 531 base pair open reading frame which encodes a polypeptide of 177 aminoacids and 19,392 daltons, confirmed by minicell analysis. Its sequence differed from previously published work in four positions. Three of the changes did not alter the aminoacid sequence while the fourth was a substitution of an alanine by a proline. The second gene, an AAC(3)II encoded by aacC2, resulted from the translation of an 858 base pair open reading frame, which encoded a 286 aminoacid polypeptide of 31,574 daltons and was identical to those from plasmids isolated in Germany and the United States. However, the homology was broken in a position between the -10 and -35 promoter sequences, which resulted in different -35 hexanucleotides and levels of resistance conferred. The assay of both genes as molecular probes has revealed their specificity with respect to other aac genes, although their usefulness was limited in the case of aacC1 derived sequences to isolated plasmid DNA, since it hybridized under stringent conditions with chromosomal DNA of some strains of E. coli.