The RhHB1/RhLOX4 module affects the dehydration tolerance of rose flowers(Rosa hybrida)by fine-tuning jasmonic acid levels

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 Iγ-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.

The OsFTIP6-OsHB22-OsMYBR57 module regulates drought response in rice

Plants have evolved a sophisticated set of mechanisms to adapt to drought stress.Transcription factors play crucial roles in plant responses to various environmental stimuli by modulating the expression of numerous stress-responsive genes.However,how the crosstalk between different transcription factor families orchestrates initiation of the key transcriptional network and the role of posttranscriptional modification of transcription factors,especially in cellular localization/trafficking in response to stress in rice,remain still largely unknown.In this study,we isolated an Osmybr57 mutant that displays a drought-sensitive phenotype through a genetic screen for drought stress sensitivity.We found that OsMYBR57,an MYB-related protein,directly regulates the expression of several key drought-related OsbZ/Ps in response to drought treatment.Further studies revealed that OsMYBR57 interacts with a homeodomain transcription factor,OsHB22,which also plays a positive role in drought signaling.We further demonstrate that OsFTIP6 interacts with OsHB22 and promotes the nucleocytoplasmic translocation of OsHB22 into the nucleus,where OsHB22 cooperates with OsMYBR57 to regulate the expression of drought-responsive genes.Our findings have revealed a mechanistic framework underlying the OsFTIP6-0sHB22-0sMYBR57 module-mediated regulation of drought response in rice.The OsFTIP6-mediated OsHB22 nucleocytoplasmic shuttling and OsMYBR57-0sHB22 regulation of OsbZIP transcription ensure precise control of expression of OsLEA3 and Rab21,and thereby regulate the response to water deficiency in rice.

Regulation of rose petal dehydration tolerance and senescence by RhNAP transcription factor via the modulation of cytokinin catabolism

Petals and leaves share common evolutionary origins but have different phenotypic characteristics,such as the absence of stomata in the petals of most angiosperm species.Plant NAC transcription factor,NAP,is involved in ABA responses and regulates senescence-associated genes,and especially those that affect stomatal movement.However,the regulatory mechanisms and significance of NAP action in senescing astomatous petals is unclear.A major limiting factor is failure of flower opening and accelerated senescence.Our goal is to understand the finely regulatory mechanism of dehydration tolerance and aging in rose flowers.We functionally characterized RhNAP,an AtNAP-like transcription factor gene that is induced by dehydration and aging in astomatous rose petals.Cytokinins(CKs)are known to delay petal senescence and we found that a cytokinin oxidase/dehydrogenase gene 6(RhCKX6)shares similar expression patterns with RhNAP.Silencing of RhNAP or RhCKX6 expression in rose petals by virus induced gene silencing markedly reduced petal dehydration tolerance and delayed petal senescence.Endogenous CK levels in RhNAP-or RhCKX6-silenced petals were significantly higher than those of the control.Moreover,RhCKX6 expression was reduced in RhNAP-silenced petals.This suggests that the expression of RhCKX6 is regulated by RhNAP.Yeast one-hybrid experiments and electrophoresis mobility shift assays showed that RhNAP binds to the RhCKX6 promoter in heterologous in vivo system and in vitro,respectively.Furthermore,the expression of putative signal transduction and downstream genes of ABA-signaling pathways were also reduced due to the repression of PP2C homolog genes by RhNAP in rose petals.Taken together,our study indicates that the RhNAP/RhCKX6 interaction represents a regulatory step enhancing dehydration tolerance in young rose petals and accelerating senescence in mature petals in a stomata-independent manner.