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Main conclusion: The results provide a significant verification of functional redundancy and diversity of CUC/NAM genes in legumes.The CUP-SHAPED COTYLEDON/NO APICAL MERISTEM (CUC/NAM) orthologs play key roles for plant organ boundary formation and organ development. Here, we performed a forward screen of the gamma irradiation mutagenesis population in mungbean and characterised a mutant, reduced rachis and fused leaflets (rrf1), which gave rise to the formation of compound leaves with reduced rachis and fused leaflets. Map-based cloning revealed that RRF1 encoded a CUC/NAM protein in mungbean. Phylogenetic analysis indicated that legume CUC1/CUC2 genes were classified as belonging to two subclades, and there are different copies of CUC1/CUC2 genes in legumes. Transcriptomic analysis showed that expression levels of a set of developmental regulators, including class I KNOTTED-LIKE HOMEOBOXI (KNOXI) gene and LATERAL ORGAN BOUNDARIES DOMAIN (LBD) gene, were altered in rrf1 mutants compared to the wild-type plants. Furthermore, rrf1 genetically interacted with heptafoliate leaflets1 (hel1), a mutant displaying a seven-leaflet compound leaf, to regulate leaf development in mungbean. Our results suggest functional redundancy and diversity of two subclades of CUC1/CUC2 genes in legumes, following the duplication of an ancestral gene. [ABSTRACT FROM AUTHOR]

Mungbean (Vigna radiata L.) is a fast-growing warm-season legume crop widely distributed in Asia. A large amount of self-shading of mungbean plants could reduce its seed yield. Thus, modification of the leaflet type could affect the leaf canopy and improve yield. In this study, a classical locus, lobed leaflet margins (lma) in mungbean, was investigated, which was controlled by a semi-dominant allele. In order to map the lma, the whole genomes of AL127 carrying lma and another accession Sulu with oval leaflets were re-sequenced; 236,998 single nucleotide polymorphisms and 8896 insertion/deletions (InDels) were identified between the two accessions. Using the validated InDels and SNP markers, lma was mapped to a syntenic region about 376 kb on chromosome 3 in mungbean and on chromosome 1 in common bean, respectively. Our results provided a framework for map-based gene cloning in mungbean. Cloning the lma should shed light on the underlying molecular mechanism controlling leaf shape in legumes and further provide the molecular basis for genetic improvement on legume crops. [ABSTRACT FROM AUTHOR]