Molecular cloning and characterization of S‐adenosyl‐methionine decarboxylase genes from mustard (Brassica juncea)

Abstract

is a key enzyme involved in the polyamine (PA) biosynthetic pathway. An understanding of how SAMDC genes are regulated is important for elucidating the molecular basis of PA biosynthesis and the role of PAs in plant growth and development. However, information regarding transcriptional regulation of SAMDC has been limited. In an attempt to address this question, we isolated four cDNAs from mustard (Brassica juncea), designated BJSAMDC1, BJSAMDC2, BJSAMDC3 and BJSAMDC4, encoding predicted SAMDC. A comparison of deduced amino acid sequence revealed that they are highly homologous to other plant SAMDCs. These proenzymes also possess the conserved cleavage domain and putative PEST sequence for SAMDC. Northern analysis showed that the SAMDC transcripts were most abundant in reproductive organs and roots but that the level was low in young leaves and petioles. Meanwhile, SAMDC expression in the leaf was up-regulated differentially in response to stress such as chilling and exogenous ACC. The effect of exogenous PAs on SAMDC expression appears to be divergent. While putrescine up-regulated the expression of BJSAMDC1, spermidine and spermine down-regulated its expression. Furthermore, mannitol was also shown to up-regulate SAMDC expression in a gene-specific manner, in which the BJSAMDC1 transcript increases but other SAMDC transcripts are not affected.

Modulation of spermidine and spermine levels in maize seedlings subjected to long-term salt stress

“…In addition to the spermidine synthase genes, the maize samdc gene was also up-regulated at 1 day of salt-stress. Changes in the samdc gene expression pattern have been reported during different stages of plant development [30] and in response to abiotic stress conditions [18,30,34]. In the case of the adc gene no apparent changes in the expression pattern were observed, although many reports support the participation of this gene in the plant salt stress response [15,19,31,44].…”

“…Brassica species such as Arabidopsis thaliana and Pringlea antiscorbutica accumulate the adc2 transcript in response to salt stress [19,44], while in mustard (Brassica juncea) the adc3 transcript is accumulated in this response [31]. In the case of samdc genes, an up-regulation was observed while treating mustard leaves with 400 mM of NaCl [18]. In a previous work, we reported the up-regulation of two maize spds transcripts (Zmspds2A and Zmspds2B), both generated by alternative splicing, in a detached leaf system with short-term salt treatments [37].…”

Differential expression of the ornithine decarboxylase gene during carposporogenesis in the thallus of the red seaweed Grateloupia imbricata (Halymeniaceae)

“…spatial) and timedependent (i.e. temporal) gene expression is assumed to be common in higher plants, and has been reported specifically for the genes of polyamine metabolism (Tarenghi and Martin-Tanguy, 1995;Michael et al, 1996;Nam et al, 1997;Carbonell, 1998, 1999a, b;Hu et al, 2005). To our knowledge, this transcriptomic evidence is new in seaweeds, likely due to the little attention paid to investigations at the molecular level.…”

Regulation of polyamine metabolism and biosynthetic gene expression during olive mature-fruit abscission

“…PA biosynthetic genes have been successfully cloned from several plant species (Carbonell and Blázquez 2009;Shao et al 2011), and their organ tissuespecific expression patterns have been characterized in some cases (Shao et al 2011). PA biosynthesis enzymes are controlled at transcriptional, translational, and posttranslational levels (Hu et al 2005). Changes in plant PA biosynthetic enzyme activities and gene expression are regulated separately, depending on physiological and developmental conditions (Bagni and Tassoni 2001;Kusano et al 2008;Carbonell and Blázquez 2009;Shao et al 2011), and SAMDC was found to be an important enzyme in the regulation of PA homeostasis (Kusano et al 2008;Mattoo et al 2010).…”