HaVTE1 confers ABA insensitivity by blocking the ABA signaling pathway in sunflowers (Helianthus annuus L.)

Sunflower (Helianthus annuus) is the fourth major oilseed crop in the world, with remarkable tolerance in saline-alkali soils. The VTE1 gene encodes tocopherol cyclase (TC), an enzyme pivotal in the biosynthesis of both vitamin E and vitamin K1. Despite its integral role in the synthesis of these crucial vitamins, the functional analysis of VTE1 under abiotic stress in sunflowers remains scant. In the present investigation, a structural analysis of the VTE1 protein across 155 diverse species revealed a highly conserved evolutionary trace. The expression profiling of HaVTE1 depicted that the HaVTE1 was responsive to the ABA pathway. Transgenic results confirmed that overexpression of HaVTE1 in Arabidopsis and sunflower showed decreased sensitivity to ABA while knocking-down in sunflower exhibited the opposite phenotype. Furthermore, biochemical experiments displayed that HaVTE1 decreases ABA sensitivity by scavenging superoxide contents. Concurrently, the transcriptome analysis revealed that HaVTE1 blocked the upstream of the ABA signaling cascade, which was further confirmed by luciferase assay, resulting in reduced sensitivity to ABA of HaVTE1 overexpression plants. The findings shed light on a theoretical basis for the sunflower responses to ABA signaling and abiotic stresses.