The molecular basis for an ancient colour mutant in sweet pea (Lathyrus odoratus)

Abstract

The classic A1 locus in sweet pea (Lathyrus odoratus) was investigated by Bateson, Punnett, and Saunders in the early 20th century history of Mendelian genetics. The mutation, in the form of the pink and white cultivar 'Painted Lady', is known from the 18th century. We show that this locus is associated with a single base pair mutation (332 G/A) in the flavonoid 3′,5′-hydroxylase (F3′5′H) gene. This results in an amino acid change (111 glycine/ aspartic acid) in the conserved substrate recognition site 1 of the enzyme. The mutant flower lacks the blue pigment delphinidin and is thus pink and white, rather than purple and blue as in the wild-type. This single amino acid change at a functionally important site appears to convert the enzyme from primary F3′5′H activity to a relatively efficient F3′H, as suggested by heterologous transformation into Arabidopsis PAP1D (a mutant line that produces anthocyanin constitutively).Résumé : Bateson, Punnet et Saunders ont étudié le locus A1 classique du pois de senteur (Lathyrus odoratus) au début du 20 e siècle, quand la génétique mendélienne en était à ses débuts. La mutation, en l'occurrence le cultivar rose et blanc Painted Lady, remonte au 18 e siècle. Les auteurs montrent que le locus est associé à la mutation d'un seule paire de bases (332 G/A) du gène codant la flavonoïde 3′,5′-hydroxylase (F3′5′H). Cette mutation entraîne la modification d'un acide aminé (111 glycine/acide aspartique) au site 1 de reconnaissance du substrat (SRS1) de l'enzyme. La fleur mutante est dépourvue de delphinidine, le pigment bleu, ce qui lui confère une couleur rose et blanche, plutôt que mauve et bleue, comme chez le type sauvage. La modification de cet unique acide aminé à un site fonctionnellement important semble transformer la protéine F3′5′H, à l'activité enzymatique rudimentaire, en protéine F3′H passablement efficace, comme le suggère la transformation hétérologue de la lignée PAP1D d'Arabidopsis (lignée mutante qui synthétise par définition de l'anthocyanine). [Traduit par la Rédaction]

The Common Bean V Gene Encodes Flavonoid 3′5′ Hydroxylase: A Major Mutational Target for Flavonoid Diversity in Angiosperms

“…A single nucleotide change was detected in a second pink-flowered b mutant that resulted in a single amino acid change (G → E) of glycine residue five in SRS1 that is invariant in all legume F3′5′H proteins ( Supplementary Figure S1 ). The importance of this amino acid was further demonstrated in sweet pea ( Lathyrus odoratus ) where a pink-flowered mutant of the classic A1 gene ( Punnett, 1923 ), which also encodes F3′5′H ( Xue and Cronk, 2017 ), contains the same G → E SRS1 substitution observed in the P. sativum mutant. Finally, the P. vulgaris 5-593 F3′5′H protein and its ortholog in the black-seeded tepary bean ( P. acutifolius A.…”

The biochemical and molecular investigation of flower color and scent sheds lights on further genetic modification of ornamental traits in Clivia miniata

“…Firstly, functional loss of structural genes usually results in an evolutionary color transition from blue to red or colored to colorless between species, as loss of function is often easier than gain of function [ 54 ]. Secondly, the expression and enzymatic properties of F3′H, F3′5′H, and DFR determine branches of the anthocyanin pathway, further affecting flower coloration diversity [ 55 , 56 ]. The enzymatic properties of enzymes at bifurcations of the flavonoid pathway may also influence flower coloration.…”

“…Firstly, F3′5′H homologs failed to be identified from C. miniata , which corresponded well with the fact that no delphinidin-derived anthocyanins were detected in this plant ( Figs 1 – 3 ; Supplementary Data Table S1 ). It is accepted that F3′5′H evolved from an F3′H precursor and a small number of amino acid exchanges would be enough for the change from 3′- to 3′,5′-hydroxylation activity [ 56 , 63 ]. However, it is unclear whether the potential CmF3′5′H is lost in the C. miniata genome or silenced in the detected tissues or organs.…”