Phaseolus ENOD40 is involved in symbiotic and non-symbiotic organogenetic processes: expression during nodule and lateral root development

Abstract

ENOD40 is an early nodulin gene, recently isolated from legume species forming nodules either after Rhizobium infection or spontaneously. ENOD40 cDNAs from Phaseolus plants were isolated and nucleotide sequence determination revealed 85% and 88.5% homology with the reported soybean cDNA clones. The putative polypeptide deduced coincides with the soybean one but a stop codon, almost in the middle of the respective ORF, renders it much shorter. This polypeptide was overexpressed as a fusion protein in Escherichia coli. Although the spatial expression pattern of the gene in the root pericycle and nodule primordium at early stages of development as well as in the pericycle of the vascular bundles and uninfected cells in mature nodules is comparable to the gene's expression pattern in soybean, differences in developmental regulation are evident. We have shown that ENOD40 transcripts are also detected at very early stages of lateral root development, in the dividing pericycle cells of the root stele that give rise to the lateral root primordia. The presence of Rhizobium causes an enhancement of the gene's expression and also induction of the gene in the vascular tissues of developed lateral roots. Interestingly, a discrimination on the gene's expression level in adventious and acropetal incipient lateral root primordia, emerging in infected and uninfected roots, is observed. This indicates that the gene's product may be involved in the hormonal status of the plant and that ENOD40 may be used as a molecular marker in lateral root initiation.

The White Clover enod40 Gene Family. Expression Patterns of Two Types of Genes Indicate a Role in Vascular Function

“…The presence of enod40 transcripts in developing lateral roots (Papadopoulou et al, 1996) and embryonic tissues (Flemetakis et al, 2000), together with our findings of Trenod40 expression during early stages of nodal root and lateral shoot development support the hypothesis for a role of enod40 in lateral organ development.…”

“…Two new sites of expression were detected in the developing lateral organs of the shoot: adventitious nodal roots, with a pattern of expression similar to that described for lateral roots (Papadopoulou et al, 1996), and developing lateral shoots, with the expression of Trenod40-3 being more prominent and induced both at early and later stages of lateral shoot development. Thus, Trenod40 genes are potentially useful molecular markers in studies of nodal root and lateral shoot development.…”

“…When multiple enod40 genes have previously been isolated from legume species, such as soybean (Kouchi and Hata, 1993), French bean (Papadopoulou et al, 1996), alfalfa (Fang and Hirsch, 1998), S. rostrata (Corich et al, Figure 6. Localization of GUS activity in transgenic white clover plants containing the pRD40-2 construct.…”

“…Expression of enod40 genes is not confined to nodules, because transcripts have been detected in nonsymbiotic meristematic tissues, such as developing lateral roots (Asad et al, 1994;Papadopoulou et al, 1996;Fang and Hirsch, 1998), young leaf and stipule primordia (Asad et al, 1994;Corich et al, 1998), stem and root procambial cells (Asad et al, 1994;Corich et al, 1998), and embryonic tissues, namely ovules and embryos (Flemetakis et al, 2000). Enod40 gene homologs have also been identified in the non-legume species, tobacco (Nicotiana tabacum; Matvienko et al, 1996) and rice (Oryza sativa; Kouchi et al, 1999), indicating a more general role in plants.…”

Modification of soybean sucrose synthase by S-thiolation with ENOD40 peptide A

“…The plant gene ENOD40 is one of the earliest nodulin genes specifically induced by nodulation factor-secreting rhizobia and appears to play an important role in root nodule organogenesis. Expression of this gene is not confined to nodules, because ENOD40 transcripts have been detected also in non-symbiotic tissues, such as developing lateral roots [11][12][13], young leafs [11], and stem cells [11,14,15]. In situ hybridization studies revealed that ENOD40 transcripts accumulate in vascular bundles of mature plant organs, mainly at sites of intensive lateral transport, suggesting a role in vascular tissue function [14][15][16].…”