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 Class Ⅲ peroxidase gene OsPrx30,transcriptionally modulated by the AT-hook protein OsATH1, mediates rice bacterial blight-induced ROS accumulation

Class Ⅲ peroxidases(CⅢ Prxs) play critical roles in plant immunity by scavenging reactive oxygen species(ROS). However, the functions of CⅢ Prxs in rice(Oryza sativa L.) immunity are largely unexplored. Here, we report a Prx precursor, OsPrx30,that is responsive to the bacterial blight Xanthomonas oryzae pv. oryzae(Xoo). OsPrx30 was primarily expressed in rice roots, leaves, and stems,and its protein product was mainly localized at the endoplasmic reticulum. Overexpression of OsPrx30 enhanced the plant’s susceptibility to Xoo by maintaining a high level of peroxidase(POD) activity and reducing the content of H2O2, whereas depletion of OsPrx30 had the opposite effects. Furthermore, we identified an AT-hook transcription factor, Os ATH1, that is specifically bound to the OsPrx30 promoter. As observed in plants overexpressing OsPrx30, depletion of Os ATH1 enhanced susceptibility to Xoo. Finally, we demonstrated that depletion of Os ATH1 increased histone H3 acetylation at the AT-rich region of the OsPrx30 promoter.Taken together, these results reveal a mechanism underlying the POD-induced natural resistance to bacterial diseases and suggest a model for transcription regulation of Prx genes in rice.