Translational and post-translational regulation of polyamine metabolic enzymes in plants.

Polyamines are small organic and basic polycations that perform essential regulatory functions in all living organisms. Fluctuations in polyamine content have been observed to occur during growth, development and under stress conditions, implying that polyamines play pivotal roles in diverse cellular and physiological processes. To achieve polyamine homeostasis, the entire metabolic pathway is subjected to a fine-tuned regulation of its biosynthetic and catabolic genes and enzymes. In this review, we describe and discuss the most important mechanisms implicated in the translational and post-translational regulation of polyamine metabolic enzymes in plants. At the translational level, we emphasize the role of polyamines in the modulation of upstream open reading frame (uORF) activities that control the translation of polyamine biosynthetic and catabolic mRNAs. At the post-translational level, different aspects of the regulation of polyamine metabolic proteins are depicted, such as the proteolytic activation of enzyme precursors, the importance of dimerization in protein stability as well as in protein intracellular localization.

Differential expression of Phaseolus vulgaris genes induced during the interaction with Rhizoctonia solani.

Common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption; however, bean production is affected by several diseases such as Rhizoctonia root rot. Few bean cultivars have been identified that effectively resist the attack of this fungus. Herein, we used the P. vulgaris Pv-2094 landrace, which is less susceptible to Rhizoctonia root rot, for the construction of a suppressive subtractive hybridization cDNA library in order to isolate plant defense-related genes. Total RNAs obtained after 8 and 16 h from inoculated and non-inoculated roots with R. solani Kühn, were used as the source of the "tester" and the "driver" samples, respectively. A total of 136 unigenes were obtained and classified into 12 functional categories. Six unigenes were selected to analyze for differential expression by qRT-PCR, including a receptor-like kinase (PvRK20-1), an acid phosphatase associated to defense (PA), a pathogenesis related protein (PR1), an ethylene responsive factor (ERF), a polygalacturonase inhibitor protein (PGIP), and an alpha-dioxygenase (α-DOX). These genes were found to be differentially expressed in a time-dependent manner in bean roots during the interaction with R. solani. Data generated from this study will contribute to the understanding of the molecular mechanisms associated with plant defense against root rot in common bean.