Differential effects of phytohormones on ethylene biosynthesis in etiolated crops

Abstract Plants adapt and survive through intricate interactions among multiple phytohormones that regulate responses to internal and external stimuli. Among these, ethylene plays a crucial role, mediating developmental and environmental signaling pathways throughout the life cycle of the plant, from seed germination to growth, maturation, and senescence. This ethylene biosynthetic pathway is tightly regulated, and recent studies report detailed mechanisms by which auxin and brassinosteroids enhance ethylene production in Arabidopsis and rice. Other phytohormones are also known to modulate ethylene biosynthesis, increasing or suppressing its biosynthesis. Besides rice, wheat, maize, barley, and sorghum represent important cereal crops. However, unlike in rice, the mechanisms underlying ethylene biosynthesis and its regulation in these crops remain poorly understood. This study demonstrated that various plant hormones can regulate ethylene biosynthesis through ethylene content measurements and phenotypic observations. Similar to rice, treatments with brassinosteroids, cytokinin, auxin, or gibberellin increased ethylene biosynthesis in etiolated seedlings in wheat, maize, barley, and sorghum. Specifically, the application of brassinosteroid, cytokinin, or auxin induced a biphasic response in monocot plants. Similar to rice, treatments with salicylic acid, jasmonic acid, or abscisic acid decreased ethylene biosynthesis in these crops. These findings offer valuable insights into the mechanisms underlying ethylene biosynthesis and its regulation by phytohormones in cereal crops.