Abstract
Previous works have shown the existence of protein partnerships belonging to a MultiStep Phosphorelay (MSP) in Populus putatively involved in osmosensing. This study is focused on the identification of a histidine-aspartate kinase, HK1b, paralog of HK1a. The characterization of HK1b showed its ability to homo- and hetero-dimerize and to interact with a few Histidine-containing Phosphotransfer (HPt) proteins, suggesting a preferential partnership in poplar MSP linked to drought perception. Furthermore, determinants for interaction specificity between HK1a/1b and HPts were studied by mutagenesis analysis, identifying amino acids involved in this specificity. The HK1b expression analysis in different poplar organs revealed its co-expression with three HPts, reinforcing the hypothesis of partnership participation in the MSP in planta. Moreover, HK1b was shown to act as an osmosensor with kinase activity in a functional complementation assay of an osmosensor deficient yeast strain. These results revealed that HK1b showed a different behaviour for canonical phosphorylation of histidine and aspartate residues. These phosphorylation modularities of canonical amino acids could explain the improved osmosensor performances observed in yeast. As conserved duplicates reflect the selective pressures imposed by the environmental requirements on the species, our results emphasize the importance of HK1 gene duplication in poplar adaptation to drought stress.
Highlights
Water deficit is one of the most important environmental stresses affecting plant growth
Activated Hog1p Mitogen-Activated Protein (MAP) kinase is essential for glycerol accumulation, re-establishing cellular turgor pressure to allow the survival of yeast cells under hyper-osmotic stress conditions [8]
The Arabidopsis hybrid-type histidine-aspartate kinase AHK1, a plasma membrane protein, is able to perceive the osmotic stress in yeast and activate the High-Osmolarity Glycerol (HOG) pathway leading to the proposal of AHK1 as an osmosensor [18,19]
Summary
Water deficit is one of the most important environmental stresses affecting plant growth. Kinase pathway leading to osmotic responses [2,3] This HOG pathway is controlled by two upstream osmosensing branches—Sln1p and Sho1p branches—wherein a classical MultiStep Phosphorelay (MSP) system ruled by a Sln1p receptor is acting [4,5]. The Arabidopsis hybrid-type histidine-aspartate kinase AHK1, a plasma membrane protein, is able to perceive the osmotic stress in yeast and activate the HOG pathway leading to the proposal of AHK1 as an osmosensor [18,19]. Mutagenesis analysis of HK1b allowed us to pinpoint a non-classical phosphorylation site and functional divergence for these two paralogs All these data gave us some new evidence that genes duplication can lead to functional divergence and that MSP genes duplication could be important for plant adaptation
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call