Disruption of ethylene signaling by suppression of ETHYLENE INSENSITIVE2 improves stomatal functionality through adjustment of ABA homeostasis and flavonoid levels

ETHYLENE INSENSITIVE2 (EIN2), an integral membrane protein and a central positive regulator of ethylene responses, plays a key role in the ethylene signaling pathway. It mediates in cross-talk between abscisic acid (ABA) and ethylene pathways. The interplay between these two stress phytohormones is a major determinant cut flower's vase life, but the details of this interplay have not been elucidated. The crosstalk between ABA homeostasis and the ethylene signaling pathway in growth, stomatal aperture regulation, photosynthesis, water loss, and senescence during ethylene-induced senescence were studied in carnation wild type and EIN2 -suppressed plantlets. Our findings revealed a significant role for EIN2 in determination of plant size (internode size and apical meristem growth). Ethylene reduced anthocyanin and elevated flavenol content, whereas EIN2 suppression changed the color of petals from white (in wild type plant) to pale yellow. The EIN2 suppression improved flower longevity and reduced senescence in carnation cut flowers under the presence of ethylene by regulation of senescence-related genes. Decrease in flavenol accumulation in EIN2 -suppressed plantlets caused ROS accumulation, which is a signal for stomatal closure. Photosynthetic capacity of EIN2 -suppressed plantlets was higher than that of wild type plantlets. EIN2 -suppressed plantlets showed smaller stomata and lower stomatal densities than the stomata of wild-type plantlets. Senescence-related genes were down-regulated by EIN2 suppression. Expression of genes involved in ABA biosynthesis/catabolism were down/up-regulated by ethylene exposure in wild-type, while remained constant in EIN2 -suppressed plantlets. In conclusion, antagonistic effects of ethylene on ABA-related responses were removed in EIN2 -suppressed plantlets. These findings elucidate mechanisms underlying limited vase life of flowers harvested with leaves and pave the way of extending vase life of cut flowers. • EIN2 regulates genes expression related to ABA homeostasis in carnation • Inhibition of ethylene signaling affects stomatal aperture regulation • EIN2 suppression reduces the negative regulation of anthocyanin accumulation • Inhibition of EIN2 gene probably induces the increase of shoot length