A novel mutation in TFL1 homolog affecting determinacy in cowpea (Vigna unguiculata)

Abstract

Mutations in the widely conserved Arabidopsis Terminal Flower 1 (TFL1) gene and its homologs have been demonstrated to result in determinacy across genera, the knowledge of which is lacking in cowpea. Understanding the molecular events leading to determinacy of apical meristems could hasten development of cowpea varieties with suitable ideotypes. Isolation and characterization of a novel mutation in cowpea TFL1 homolog (VuTFL1) affecting determinacy is reported here for the first time. Cowpea TFL1 homolog was amplified using primers designed based on conserved sequences in related genera and sequence variation was analysed in three gamma ray-induced determinate mutants, their indeterminate parent "EC394763" and two indeterminate varieties. The analyses of sequence variation exposed a novel SNP distinguishing the determinate mutants from the indeterminate types. The non-synonymous point mutation in exon 4 at position 1,176 resulted from transversion of cytosine (C) to adenine (A) leading to an amino acid change (Pro-136 to His) in determinate mutants. The effect of the mutation on protein function and stability was predicted to be detrimental using different bioinformatics/computational tools. The functionally significant novel substitution mutation is hypothesized to affect determinacy in the cowpea mutants. Development of suitable regeneration protocols in this hitherto recalcitrant crop and subsequent complementation assay in mutants or over-expressing assay in parents could decisively conclude the role of the SNP in regulating determinacy in these cowpea mutants.

Genetic control of inflorescence architecture in legumes

“…Mutants with determinate inflorescences have been described in other grain legumes. In the last years, the underlying mutations of some of these phenotypes have been identified, and these have been shown to affect DET / PsTFL1a homologs ( Avila et al, 2007 ; Liu et al, 2010 ; Repinski et al, 2012 ; Dhanasekar and Reddy, 2014 ; Mir et al, 2014 ). An exception to this is the soybean dt2 mutants, which show a semideterminate phenotype that is not caused by a mutation in a TFL1 -like gene.…”

“…Diverse evidence suggests that, indeed, the properties and architecture of this network could be conserved among grain legumes. The determinate growth habit caused by mutations in DET/TFL1 -homologs in other grain legumes indicates that DET function is conserved in these species ( Liu et al, 2010 ; Tian et al, 2010 ; Kwak et al, 2012 ; Repinski et al, 2012 ; Dhanasekar and Reddy, 2014 ). Also, the characterization of MtPIM , the M. truncatula homolog of PIM , indicates conservation of this function in Medicago ( Benlloch et al, 2006 ).…”

“…Also, determinate cultivars are sometimes preferred because this growth habit facilitates mechanical harvesting ( Kelly, 2001 ; Boote et al, 2003 ). As described above, recessive mutations in homologs of the Arabidopsis TFL1 gene underlie this determinate trait, at least in the grain legume crops where the genetic basis of the phenotype has been elucidated ( Foucher et al, 2003 ; Avila et al, 2007 ; Liu et al, 2010 ; Repinski et al, 2012 ; Dhanasekar and Reddy, 2014 ).…”

Major Contribution of Flowering Time and Vegetative Growth to Plant Production in Common Bean As Deduced from a Comparative Genetic Mapping

“…Recent findings have clearly shown that in several legume species, determinate inflorescence architecture is conferred by mutation of specific TFL1 genes (Benlloch et al, 2015). The determinate growth habit caused by mutations within specific TFL1 -homologs in other grain legumes indicates that the determinate function is conserved in these species (Kong et al, 2010; Tian et al, 2010; Kwak et al, 2012; Repinski et al, 2012; Dhanasekar and Reddy, 2014). …”

Winged bean (Psophocarpus tetragonolobus (L.) DC.) for food and nutritional security: synthesis of past research and future direction

“…Perhaps, TILLING (targeting induced local lesions in genomes) or ecoTILLING are possible approaches to obtain determinate growth phenotypes, although this method requires sequence information of target genes. The genomic basis of a determinate shoot apex meristems has been uncovered in other leguminous crops; for example, soybean (Tian et al 2010), chickpea (Hegde 2011), common bean (Kwak et al 2012;Repinski et al 2012), and cowpea (Dhanasekar and Reddy 2015), where the determinate shoot phenotypes are reported to be related to mutations in genes orthologous with the A. thaliana TERMINAL FLOWER1 (TFL1) genes. Such information could be used to identify candidate genes involved in the same mechanism in winged bean and to define the target for TILLING methods.…”