Effect of salt stress on the regulation of maize (Zea mays L.) genes involved in polyamine biosynthesis.

MARGARITA RODRÍGUEZ-KESSLER, ANGEL G. ALPUCHE-SOLÍS, OSCAR A. RUIZ & JUAN F. JIMÉNEZ-BREMONT

PLANT GROWTH REGULATION

Año: 2006 vol. 48 p. 175 - 185

0167-6903

A cDNA for spermidine synthase (SPDS), which converts putrescine to the higher polyamine spermidine using decarboxylated S-adenosylmethionine as a cofactor, was isolated from Zea mays leaves (Zmspds2). Comparison of the deduced amino acid sequence revealed a high homology (81.9%) with Oryza sativa SPDS2. RT-PCR analyses showed that Zmspds2 was equally expressed in leaves, stem and roots. In contrast, transcripts of other genes related to polyamine biosynthesis (Zmodc, adc and samdc) showed tissue-specific regulation. We analysed the effect of salt-stress on the expression of all these genes in maize leaves exposed to NaCl solutions of different concentrations. Our results showed that only Zmodc and Zmspds2 were up-regulated by salt stress; whereas the other two genes were barely affected by this treatment. In addition to Zmspds2, a second transcript encoding a maize SPDS (ZmspdsSS) that also became up-regulated by salt stress, was identified in this studies. Comparison of partial sequences of both transcripts (Zmspds2 and ZmspdsSS) with the corresponding genomic DNA region suggests that both transcripts might be derived from the same gene (Zmspds2) by alternative splicing.