Hormonal regulation of Freesia cutflowers and FhACS1

The differential transcriptional responses of a freesia 1-aminocyclopropane-l-carboxylate synthase gene (FhACS1) to exogenous ethephon, abscisic acid (ABA), salicylic acid (SA), indole-3-acetic acid (IAA), 6-benzylaminopurine (6-BA), silver thiosulfate (STS) and sugar were studied using real-time quantitative PCR. Pretreatments for periods of 24 h were evaluated in bud 3 and bud 6 on the inflorescence during freesia flower development and senescence. The results showed that individual exogenous pretreatment with ethephon, IAA, ABA and SA all resulted in the accelerated senescence of freesia flowers compared to those of control buds. Ethephon enhanced FhACS1 expression and extended this high expression; IAA induced an earlier and higher accumulation of FhACS1 transcripts in bud 3, held-up FhACS1 transcript accumulation in later development in bud 6; ABA evidently stimulated a stronger and earlier response of FhACS1 and SA led a higher and longer FhACS1 transcript accumulation. Conversely, 6-BA, STS and sugar pretreatments had a positive effect on the flower development and downregulated FhACS1 expression. Among these treatments, 6-BA significantly restrained the accumulation of the FhACS1 transcript, especially in bud 6; STS also lowered the FhACS1 transcription level overall; while sugar postponed the arrival of the FhACS1 expression peak and significantly decreased the amount of FhACS1 transcript. These results show that these phytohormones and chemical substances signals lead to transcriptional regulation of FhACS1, conjecturing that FhACS1 may participate in the complex hormonal and developmental net works in freesia flower senescence.

► Effects of phytohormone on development and senescence in Freesia flowers.
► Exogenous ethephon, IAA, ABA, and SA upregulated transcription of FhACS1.
► STS, 6-BA and sugar pretreatments downregulated FhACS1 expression.
► FhACS1 may participate in the hormonal net work in freesia flower senescence.