Parallel domestication with a broad mutational spectrum of determinate stem growth habit in leguminous crops.

Stem growth habit is a key plant architecture trait determining yield potential in grain legumes, and the phenotypic change from the indeterminate stem growth habit of wild mungbeans (Vigna radiata) to the determinate stem growth habit of cultivated mungbeans is a critical domestication transition. Here we show that indeterminate stem growth in wild mungbean is modulated by a single gene, VrDet1, which encodes a signaling protein of shoot apical meristems. The transition from an indeterminate to a determinate stem growth habit was achieved by selection of two linked point mutations in two putative cis-regulatory elements, resulting in a significant reduction in gene expression. Both the wild-type nucleotides corresponding to the two point mutations were essential for VrDet1 function. In addition, two highly diverse haplotypes of Vrdet1 were found in cultivated mungbeans, suggesting dual domestication of Vrdet1. VrDet1 was orthologous to Dt1 in wild soybean and PvTFL1y in wild common bean, where multiple loss-of-function mutations altering the coding sequences of individual genes were selected to produce determinate stems in cultivated accessions. Interspecific comparison of these orthologs in the wild and cultivated accessions reveals the most conservative interspecific and intraspecific parallel domestication events with the broadest mutational spectrum of a domestication trait in leguminous crops. We also found that interspecifically and functionally conserved promoters possess cis-regulatory elements that are highly conserved in kind but greatly variable in number and order, demonstrating the evolutionary dynamics of regulatory sequences. This work provides insights into the origins of cultivated mungbean and exemplifies the conservativeness and plasticity of the domestication processes of related crops.

Molecular and transcriptional characterization of phosphatidyl ethanolamine-binding proteins in wild peanuts Arachis duranensis and Arachis ipaensis.

BACKGROUND: Phosphatidyl ethanolamine-binding proteins (PEBPs) are involved in the regulation of plant architecture and flowering time. The functions of PEBP genes have been studied in many plant species. However, little is known about the characteristics and expression profiles of PEBP genes in wild peanut species, Arachis duranensis and Arachis ipaensis, the diploid ancestors of cultivated peanuts. RESULTS: In this study, genome-wide identification methods were used to identify and characterize a total of 32 peanut PEBP genes, 16 from each of the two wild peanut species, A. duranensis and A. ipaensis. These PEBP genes were classified into 3 groups (TERMINAL FLOWER1-like, FLOWERING LOCUS T-like, and MOTHER OF FT AND TFL1-like) based on their phylogenetic relationships. The gene structures, motifs, and chromosomal locations for each of these PEBPs were analyzed. In addition, 4 interchromosomal duplications and 1 tandem duplication were identified in A. duranensis, and 2 interchromosomal paralogs and 1 tandem paralog were identified in A. ipaensis. Ninety-five different cis-acting elements were identified in the PEBP gene promoter regions and most genes had different numbers and types of cis-elements. As a result, the transcription patterns of these PEBP genes varied in different tissues and under long day and short day conditions during different growth phases, indicating the functional diversities of PEBPs in different tissues and their potential functions in plant photoperiod dependent developmental pathways. Moreover, our analysis revealed that AraduF950M/AraduWY2NX in A. duranensis, and Araip344D4/Araip4V81G in A. ipaensis are good candidates for regulating plant architecture, and that Aradu80YRY, AraduYY72S, and AraduEHZ9Y in A. duranensis and AraipVEP8T in A. ipaensis may be key factors regulating flowering time. CONCLUSION: Sixteen PEBP genes were identified and characterized from each of the two diploid wild peanut genomes, A. duranensis and A. ipaensis. Genetic characterization and spatio-temporal expression analysis support their importance in plant growth and development. These findings further our understanding of PEBP gene functions in plant species.

Characterization and Comparative Analysis of RWP-RK Proteins from Arachis duranensis, Arachis ipaensis, and Arachis hypogaea.

RWP-RK proteins are important factors involved in nitrate response and gametophyte development in plants, and the functions of RWP-RK proteins have been analyzed in many species. However, the characterization of peanut RWP-RK proteins is limited. In this study, we identified 16, 19, and 32 RWP-RK members from Arachis duranensis, Arachis ipaensis, and Arachis hypogaea, respectively, and investigated their evolution relationships. The RWP-RK proteins were classified into two groups, RWP-RK domain proteins and NODULE-INCEPTION-like proteins. Chromosomal distributions, gene structures, and conserved motifs of RWP-RK genes were compared among wild and cultivated peanuts. In addition, we identified 12 orthologous gene pairs from the two wild peanut species, 13 from A. duranensis and A. hypogaea, and 13 from A. ipaensis and A. hypogaea. One, one, and seventeen duplicated gene pairs were identified within the A. duranensis, A. ipaensis, and A. hypogaea genomes, respectively. Moreover, different numbers of cis-acting elements in the RWP-RK promoters were found in wild and cultivated species (87 in A. duranensis, 89 in A. ipaensis, and 92 in A. hypogaea), and as a result, many RWP-RK genes showed distinct expression patterns in different tissues. Our study will provide useful information for further functional and evolutionary analysis of the RWP-RK genes.

Molecular Characterization and Expression Profile Analysis of Heat Shock Transcription Factors in Mungbean.

Heat shock transcription factors (Hsfs) are essential elements in plant signal transduction pathways that mediate gene expression in response to various abiotic stresses. Mungbean (Vigna radiata) is an important crop worldwide. The emergence of a genome database now allows for functional analysis of mungbean genes. In this study, we dissect the mungbean Hsfs using genome-wide identification and expression profiles. We characterized a total of 24 VrHsf genes and classified them into three groups (A, B, and C) based on their phylogeny and conserved domain structures. All VrHsf genes exhibit highly conserved exon-intron organization, with two exons and one intron. In addition, all VrHsf proteins contain 16 distinct motifs. Chromosome location analysis revealed that VrHsf genes are located on 8 of the 11 mungbean chromosomes, and that seven duplicated gene pairs had formed among them. Moreover, transcription patterns of VrHsf genes varied in different tissues, indicating their different roles in plant growth and development. We identified multiple stress related cis-elements in VrHsf promoter regions 2 kb upstream of the translation initiation codons, and the expression of most VrHsf genes was altered under different stress conditions, suggesting their potential functions in stress resistance pathways. These molecular characterization and expression profile analyses of VrHsf genes provide essential information for further function investigation.