The role of hydrogen peroxide (H2O2) and various antioxidants in the regulation of expression of the three Cat and Gst1 genes of maize (Zea mays L.) has been investigated. Low concentrations of H2O2 appeared to inhibit Cat1, Cat3, and Gst1 gene expression, while higher doses strongly induced these genes. Time course experiments indicated that high concentrations of H2O2 induced Cat1, Cat2, and Gst1 gene expression to higher levels, and in less time, than lower H2O2 concentrations. Induction of Cat3 was superimposed on the circadian regulation of the gene. These results demonstrate a direct signaling action of H2O2 in the regulation of antioxidant gene responses in maize.The effects of the antioxidant compounds N‐acetylcysteine, pyrrolidine dithiocarbamate, hydroquinone, and the electrophile antioxidant responsive element (ARE)‐inducer β‐naphthoflavone were quite different and specific for each gene/compound/concentration combination examined. The response of each gene to each antioxidant compound tested was unique, suggesting that the ability of these compounds to affect expression of the maize Cat and Gst1 genes may not be the result of a common (antioxidant) mode of action. A putative regulatory ARE motif involved in the regulation of antioxidant and oxidative stress gene responses in mammalian systems is present in the promoter of all three maize catalase genes and we tested its ability to interact with nuclear extracts prepared from 10 days post‐imbibition senescing scutella. Protein‐DNA interactions in the ARE motif and the U2 snRNA homologous regions of the Cat1 promoter were observed, suggesting that ARE may play a role in the high induction of Cat1 in a tissue which, due to senescence, is under oxidative stress.

Alternative oxidase (Aox) has been proposed as a functional marker for breeding stress tolerant plant varieties. This requires presence of polymorphic Aox allele sequences in plants that affect plant phenotype in a recognizable way. In this review, we examine the hypothesis that organization of genomic Aox sequences and gene expression patterns are highly variable in relation to the possibility that such a variation may allow development of Aox functional markers in plants. Aox is encoded by a small multigene family, typically with four to five members in higher plants. The predominant structure of genomic Aox sequences is that of four exons interrupted by three introns at well conserved positions. Evolutionary intron loss and gain has resulted in the variation of intron numbers in some Aox members that may harbor two to four introns and three to five exons in their sequence. Accumulating evidence suggests that Aox gene structure is polymorphic enough to allow development of Aox markers in many plant species. However, the functional significance of Aox structural variation has not been examined exhaustively. Aox expression patterns display variability and typically Aox genes fall into two discrete subfamilies, Aox1 and Aox2, the former being present in all plants and the latter restricted in eudicot species. Typically, although not exclusively, the Aox1-type genes are induced by many different kinds of stress, whereas Aox2-type genes are expressed in a constitutive or developmentally regulated way. Specific Aox alleles are among the first and most intensively stressinduced genes in several experimental systems involving oxidative stress. Differential response of Aox genes to stress may provide a flexible plan of plant defense where an energy-dissipating system in mitochondria is involved. Evidence to link structural variation and differential allele expression patterns is scarce. Much research is still required to understand the significance of polymorphisms within AOX gene sequences for gene regulation and its potential for breeding on important agronomic traits. Association studies and mapping approaches will be helpful to advance future perspectives for application more efficiently.

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The fruit canning industry processes large quantities of the clingstone varieties of peach (Prunus persica L. Batch). The occurrence of split-pit formation--the opening of the pit and sometimes splitting of the fruit--causes deterioration of canned fruit quality. The frequency of split-pit formation is influenced by genetic and environmental factors. To increase understanding of the molecular mechanisms underlying split-pit formation in peach, we cloned and characterized the PPERFUL and PPERSHP genes that are homologues to the genes FRUITFULL and SHATTERPROOF, respectively, which are involved in fruit splitting (pod shattering) in Arabidopsis thaliana. The deduced amino acid sequences of the two genes had high homology with members of the MADS-box family of transcription factors, and particularly with other members of the FUL-like family of A-type MADS-box proteins and PLENA-like family of C-type MADS-box proteins, respectively. PPERFUL and PPERSHP were expressed throughout fruit development from full anthesis until fruit harvest. Differences in the mRNA abundance of each gene were compared in a split-pit sensitive and a split-pit resistant variety. Results suggested that temporal regulation of PPERFUL and PPERSHP expression may have an effect on the split-pit process.