Silencing GhCOI1 in Gladiolus hybridus increases susceptibility to Alternaria brassicicola and impairs inducible defenses

Abstract

Alternaria brassicicola is a necrotrophic pathogenic fungus that severely affects both the yield and quality of Gladiolus cut flowers and cormels. The jasmonate signaling pathway plays an important role in plant disease resistance. The protein CORONATINE INSENSITIVE 1 (COI1) is a key regulator of this pathway, and the COI1 gene can modulate jasmonate signaling-induced defenses against necrotrophic fungi. Here, we characterize a COI1 gene from Gladiolus, GhCOI1. GhCOI1 transcript levels were greatest in the leaves, followed by the roots. A low MeJA concentration promoted GhCOI1 expression, which remained high after 6\xa0h. Silencing GhCOI1 via VIGS reduced GhCOI1 transcript levels. The length of fungal hyphae and amount of fungal DNA were significantly greater in silenced plants than in control plants. Moreover, GhCOI1 was necessary for the induction of SOD, POD, PPO, and CAT in the Gladiolus defense response to A. brassicicola infestation. GhCOI1 silencing reduced the accumulation of H2O2, allowing the fungus to enter leaf tissue through stomata and cause necrosis directly. Taken together, these results suggest that GhCOI1 is an essential signaling component that controls the JA-regulated defense response against A. brassicicola in Gladiolus plants.Key messageThe results of this study reveal that silencing GhCOI1 reduced the disease resistance of Gladiolus