Hexokinase1: A glucose sensor involved in drought stress response and sugar metabolism depending on its kinase activity in strawberry

Abstract

Hexokinase1 (HXK1) is a bifunctional enzyme that plays indispensable roles in plant growth, nitrogen utilization, and stress resistance. However, information on the HXK family members of strawberries and their functions in glucose sensing and metabolic regulation is scarce. In the present study, four HXKs were firstly identified in the genome of Fragaria vesca and F. pentaphylla. The conserved domains of the HXK1s were confirmed, and a site-directed mutation (S177A) was introduced into the FpHXK1. FpHXK1, which shares the highest identity with the AtHXK1 was able to restore the glucose sensitivity and developmental defects of the Arabidopsis gin2-1 mutant, but not its kinase-activity-impaired mutant (FpHXK1S177A). The transcription of FpHXK1 was dramatically up-regulated under PEG-simulated drought stress conditions. The inhibition of the HXK kinase activity delayed the strawberry plant’s responses to drought stress. Transient overexpression of the FpHXK1 and its kinase-impaired mutant differentially affected the level of glucose, sucrose, anthocyanins, and total phenols in strawberry fruits. All these results indicated that the FpHXK1, acting as a glucose sensor, was involved in drought stress response and sugar metabolism depending on its kinase activity.

Integrative analysis of grapevine (Vitis vinifera L) transcriptome reveals regulatory network for Chardonnay quality formation

“…Yang et al ( 58 ) showed that MdFRK2 is the key gene for fructose phosphorylation in apples and the homeostasis and signaling of fructose content can regulate sugar metabolism and content. Transient overexpression of FpHXK1 and its kinase-deficient mutants had different effects on the contents of glucose, sucrose, anthocyanins and total phenols in strawberry fruit ( 59 ). F6P can re-synthesize sucrose under the catalysis of sucrose phosphate synthase (SPS).…”

The critical roles of three sugar-related proteins (HXK, SnRK1, TOR) in regulating plant growth and stress responses

“…A similar result was found in strawberry ( Fragaria pentaphylla ). Inhibition of FpHXK1 kinase activity weakened the strawberry plant’s responses to drought stress [ 25 ]. Meanwhile, about HXK2, researchers found that Arabidopsis plants transgenic for Glycine max HXK2 ( GmHXK2 ) showed improved tolerance to salt stress [ 24 ].…”

Complex Role of Photoreceptors in Light and Temperature Sensing: From Mechanism to the Target Genes Regulation. A Focus on the Genes Related to the Biosynthesis of Phenolic Compounds

“…To ensure further signaling steps, HXK1 requires interaction with other proteins. It was documented, that HXK1 can form the complex with the VHA-B (vacuolar proton pump -subunit B), or components of Polycomb Repressive Complex 2 -SWN (SWINGER), and -CLF (CURLY LEAF) [13]. Interaction of HXK1 with the CLF and SWN leads to the trimethylation of H3 lysine in the promoter region of the target genes and therefore stimulates the expression of target genes [13].…”

“…It was documented, that HXK1 can form the complex with the VHA-B (vacuolar proton pump -subunit B), or components of Polycomb Repressive Complex 2 -SWN (SWINGER), and -CLF (CURLY LEAF) [13]. Interaction of HXK1 with the CLF and SWN leads to the trimethylation of H3 lysine in the promoter region of the target genes and therefore stimulates the expression of target genes [13]. In the nucleus of Arabidopsis thaliana, the presence of glucose leads to increased degradation of EIN3 (Ethylene insensitive 3) by AtHXK1, resulting in a diminished response to ethylene-induced signaling [13].…”

“…Interaction of HXK1 with the CLF and SWN leads to the trimethylation of H3 lysine in the promoter region of the target genes and therefore stimulates the expression of target genes [13]. In the nucleus of Arabidopsis thaliana, the presence of glucose leads to increased degradation of EIN3 (Ethylene insensitive 3) by AtHXK1, resulting in a diminished response to ethylene-induced signaling [13]. In addition, MdHXK1 phosphorylates Ser361 of the MdbHLH3 protein and thus stabilizes the interaction between MdbHLH3 and MYB1-9-11, which leads to the stimulation of the anthocyanin's biosynthesis under the low-temperature conditions in Malus domestica [13].…”