The histidine phosphotransfer AHP4 plays a negative role in Arabidopsis plant response to drought

Abstract

Cytokinin plays an important role in plant stress responses via a multistep signaling pathway, involving the histidine phosphotransfer proteins (HPs). In Arabidopsis thaliana, the AHP2, AHP3 and AHP5 proteins are known to affect drought responses; however, the role of AHP4 in drought adaptation remains undetermined. In the present study, using a loss-of-function approach we showed that AHP4 possesses an important role in the response of Arabidopsis to drought. This is evidenced by the higher survival rates of ahp4 than wild-type (WT) plants under drought conditions, which is accompanied by the downregulated AHP4 expression in WT during periods of dehydration. Comparative transcriptome analysis of ahp4 and WT plants revealed AHP4mediated expression of several dehydration-and/or abscisic acid-responsive genes involved in modulation of various physiological and biochemical processes important for plant drought acclimation. In comparison with WT, ahp4 plants showed increased wax crystal accumulation in stems, thicker cuticles in leaves, greater sensitivity to exogenous abscisic acid at germination, narrow stomatal apertures, heightened leaf temperatures during dehydration, and longer root length under osmotic stress. In addition, ahp4 plants showed greater photosynthetic efficiency, lower levels of reactive oxygen species, reduced electrolyte leakage and lipid peroxidation, and increased anthocyanin contents under drought, when compared with WT. These differences displayed in ahp4 plants are likely due to upregulation of genes that encode enzymes involved in reactive

Analysis of the histidine kinase gene family and the role of GhHK8 in response to drought tolerance in cotton

“…The findings demonstrated for the first time that AHK4 was capable of interacting with AHP1, 2, 3, and 5 via a close phosphorelay reaction (Suzuki et al, 2001). Studies in Arabidopsis showed that the reaction to drought is negatively impacted by the histidine phosphotransfer AHP4 (Ha et al, 2022), AHP1, AHP2, AHP3, and AHP5 can communicate with AHK2, AHK3, and AHK4 (Dortay et al, 2006; Mähönen et al, 2006), and histidine phosphotransfer proteins from Arabidopsis AHP2, AHP3, and AHP5 serve as redundant negative regulators of the drought stress response (Nishiyama et al, 2013). This indicates that GhHK8 may participate in cotton drought control…”

NAC61 regulates late- and post-ripening osmotic, oxidative, and biotic stress responses in grapevine

“…Interestingly, an auxin efflux carrier and the ARF TF Monopteros , which inhibits stomatal development ( Zhang et al , 2014 ), were found among the NAC61 HCTs. Similarly, the down-regulation of the HCTs histidine phosphotransfer AHP4 , whose knockout narrows stomatal apertures, heightens leaf temperatures during water stress, and increases leaf RWC ( Ha et al , 2022 ), and the phosphatase PP2CA/AHG3 , whose repression activates ABA-mediated signaling pathway leading to stomatal closure and water retention ( Jung et al , 2020 ), may contribute to NAC61 function in osmotic stress responses. Interestingly, hypoxia-related genes are found among NAC61- induced DEGs, such as a Hypoxia-responsive gene and three dehydration-responsive proteins ( RD22 ), indicating a decrease in oxygen supply, likely due to water saturation of the apoplast ( van den Dries et al , 2013 ).…”

NAC61 regulates late-and post-ripening associated processes in grapes involving a NAC60-dependent regulatory network

“…Interestingly, an auxin efflux carrier and the ARF TF Monopteros, which inhibits stomatal development (Zhang et al, 2014), is found among NAC61 HCTs. Similarly, the downregulation of the HCTs histidine phosphotransfer AHP4, whose knock-out narrows stomatal apertures, heightens leaf temperatures during water stress and increases leaf RWC (Ha et al, 2022) and the phosphatase PP2CA/AHG3, whose repression activates ABA-mediated signaling pathway leading to stomatal closure and water retention (Jung et al, 2020), may contribute to NAC61 function in osmotic stress responses. Interestingly, hypoxia-related genes are found among NAC61 induced DEGs, such as a Hypoxia-responsive gene and three dehydration-responsive proteins (RD22), indicating a decrease in oxygen supply likely due to water saturation of the apoplast (van den Dries et al, 2013).…”