Accumulation of ENOD2-like Transcripts in Non-Nodulating Woody Papilionoid Legumes

Japanese pagodatree (Styphnolobium japonicum [L.] Schott) and American yellowwood (Cladrastis kentukea Dum.-Cours.) Rudd are the first woody, non-nodulating papilionoid legumes shown to possess putative early nodulin 2 (ENOD2) genes. ENOD2 cDNAs from Japanese pagodatree (807 bp) and American yellowwood (735 bp) have 75% to 79% sequence identity to ENOD2 sequences and encode deduced proteins that possess conserved ENOD2 pentapeptides (PPHEK and PPEYQ). Lower percentages of glucose and higher percentages of histidine and valine suggest that SjENOD2 and CkENOD2 are different from other ENOD2s. Hybridization analyses indicate the clones represent ENOD2 gene families of two to four genes in Japanese pagodatree and American yellowwood genomes, and ENOD2-like transcripts were detected in stems and flowers, as well as roots. Only roots of control species that nodulate, Maackia amurensis Rupr. & Maxim. and alfalfa (Medicago sativa), produced pseudonodules after treatment with zeatin or 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Accumulation of MaENOD2 transcripts was enhanced during the first 10 d of treatment, but 2,3,5-triiodobenzoic acid and zeatin enhanced transcript accumulation after 30 d in roots of Japanese pagodatree and American yellowwood. Characteristics that distinguish ENOD2 gene families in basal, non-nodulating woody legumes from other ENOD2 genes may provide new information about the function of these genes during symbiotic and non-symbiotic organ development.