Abstract
Phytohormones are key factors in plant responsiveness to abiotic and biotic stresses, and maintaining hormone homeostasis is critically important during stress responses. Cut rose (Rosa hybrida) flowers experience dehydration stress during postharvest handling, and jasmonic acid (JA) levels change as a result of this stress. However, how JA is involved in dehydration tolerance remains unclear. We investigated the functions of the JA- and dehydration-induced RhHB1 gene, which encodes a homeodomain-leucine zipper I γ-clade transcription factor, in rose flowers. Silencing RhHB1 decreased petal dehydration tolerance and resulted in a persistent increase in JA-Ile content and reduced dehydration tolerance. An elevated JA-Ile level had a detrimental effect on rose petal dehydration tolerance. RhHB1 was shown to lower the transient induction of JA-Ile accumulation in response to dehydration. In addition to transcriptomic data, we obtained evidence that RhHB1 suppresses the expression of the lipoxygenase 4 (RhLOX4) gene by directly binding to its promoter both in vivo and in vitro. We propose that increased JA-Ile levels weaken the capacity for osmotic adjustment in petal cells, resulting in reduced dehydration tolerance. In conclusion, a JA feedback loop mediated by an RhHB1/RhLOX4 regulatory module provides dehydration tolerance by fine-tuning bioactive JA levels in dehydrated flowers.
Highlights
Plants are challenged throughout their life cycle with different abiotic or biotic stresses, among which drought and dehydration are often the most limiting factors for crop production worldwide[1,2]
We previously reported that RhHB1, which belongs to the γ-clade HD-Zip I subfamily, mediates the antagonistic effect of GAs on abscisic acid (ABA) and ethylene action during rose petal senescence[47]
RhHB1 is induced by both dehydration and ABA in rose petals[44], so we investigated its possible role in dehydration tolerance
Summary
Plants are challenged throughout their life cycle with different abiotic or biotic stresses, among which drought and dehydration are often the most limiting factors for crop production worldwide[1,2]. For the production and marketing of horticultural products, drought/dehydration causes severe losses in quality and quantity[3,4]. Water loss greater than 3–5% of most fresh horticultural products results in visual symptoms, such as shriveling and skin necrosis during postharvest handling[5]. To combat these types of stress, plants have evolved. Numerous JA-related compounds have been found to accumulate in the flowers of Petunia hybrida, Cymbidium faberi, Cattleya luteola, etc.[20]. Exogenous jasmonates can promote tepal/petal senescence in Dendrobium and Petunia[21] and can delay the senescence of nonclimacteric eggplant fruit[22] and Iris flowers[23]
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