Low jasmonic acid accumulation causes the defect in the tepal expansion in double-flowered green lily cultivar, ‘Doubleen’

In this study, the mechanisms underlying green flower phenotype of a lily cultivar, ‘Doubleen’, was investigated focusing on jasmonic acid (JA) accumulation. ‘Doubleen’ is a mutant lily cultivar derived from ‘Yelloween’ and has unexpanded, non-pigmented green tepals but lacks the stamen and carpel. ‘Doubleen’ was treated with methyl jasmonate (MeJA) to investigate the subsequent change in floral organ characteristics. As a result, the tepals of MeJA-treated ‘Doubleen’ expanded and had yellow pigmentation, whereas those of the control did not. To estimate the JA synthesis site in the lily flower, the accumulation profiles of JA and jasmonoyl-L-isoleucine (JA-Ile) were compared between the floral organs of ‘Yelloween’. The JA-Ile content of carpels was the lowest of the three floral organs at all developmental stages. JA-Ile contents in the inner tepals and stamens were not significantly different in all developmental stages. To determine potential role of JA and JA-Ile in tepal expansion and pigmentation in lily flowers, the accumulation of these two compounds was compared between the tepals of ‘Yelloween’ and those of ‘Doubleen’. At all developmental stages, the tepals of ‘Doubleen’ accumulated JA at concentrations lower than those of ‘Yelloween’. Floral organ removal experiments were also conducted using ‘Yelloween’ to evaluate its effect on tepal expansion. Notably, tepal expansion was not affected by pistil removal, but was strongly suppressed by stamen removal. Overall, these results suggest the loss of JA biosynthesis site in the flowers of ‘Doubleen’ leading to the formation of unexpanded green tepals on their flowers.