Guard-Cell Hexokinase Increases Water-Use Efficiency Under Normal and Drought Conditions

Abstract

Water is a limiting resource for many land plants. Most of the water taken up by plants is lost to the atmosphere through the stomata, which are adjustable pores on the leaf surface that allow for gas exchange between the plant and the atmosphere. Modulating stomatal activity might be an effective way to reduce plants’ water consumption and enhance their productivity under normal, as well as water-limiting conditions. Our recent discovery of stomatal regulation by sugars that is mediated by guard-cell hexokinase (HXK), a sugar-sensing enzyme, has raised the possibility that HXK might be used to increase plant water-use efficiency (WUE; i.e., carbon gain per unit of water). We show here that transgenic tomato and Arabidopsis plants with increased expression of HXK in their guard cells (GCHXK plants) exhibit reduced transpiration and higher WUE without any negative effects on growth under normal conditions, as well as drought avoidance and improved photosynthesis and growth under limited-water conditions. Our results demonstrate that exclusive expression of HXK in guard cells is an effective tool for improving WUE, and plant performance under drought.

Future-Proofing Potato for Drought and Heat Tolerance by Overexpression of Hexokinase and SP6A

“…We expressed the KST::AtHXK1 construct alone and together with SP6A in potato and provided clear evidence that the desired effect of AtHXK1 expression (e.g., reduced transpiration) is also present in this crop plant under control conditions as shown for Arabidopsis ( Kelly et al, 2013 ), citrus ( Lugassi et al, 2015 ) and tomato ( Kelly et al, 2019 ). Concurrently, stomata-specific expression of AtHXK1 slightly affected photosynthetic CO 2 assimilation in potato.…”

“…Decreased transpiration rates might solve this agricultural problem. AtHXK1 was shown to reduce transpiration when expressed in guard cells of A. thaliana , citrus and tomato without a negative effect on plant growth and CO 2 assimilation ( Kelly et al, 2013 , 2019 ; Lugassi et al, 2015 ). Although the molecular mechanism is not completely understood, it is assumed that AtHXK1 controls stomatal aperture to coordinate photosynthesis with transpiration through sugar signaling pathways ( Kottapalli et al, 2018 ; Granot and Kelly, 2019 ) as it has been described as a sugar sensor before ( Moore et al, 2003 ).…”

PdGNC confers drought tolerance by mediating stomatal closure resulting from NO and H2O2 production via the direct regulation of PdHXK1 expression in Populus

“…Many studies have revealed that reduction in stomatal aperture as a result of ABA-induced NO and H 2 O 2 production improves WUE and drought tolerance (Santisree et al, 2015;Fancy et al, 2017); however, less is known about this molecular mechanism in plants. Previous studies found that elevated NO and H 2 O 2 production reduces stomatal conductance and improves WUE by c. 20% in tomato and Arabidopsis (Kelly et al, 2013(Kelly et al, , 2019. Furthermore, most studies have concentrated on herbaceous plants, with few studies considering woody plants (Yang et al, 2018).…”

“…To resist water deficit, plants respond to the stress at the molecular and cellular levels, for example by generating nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ), which are well known for their ability to induce stomatal closure (Zhang et al ., 2019; van Meeteren et al ., 2020). Stomatal closure is a common adaptation response by plants to the onset of drought conditions, one that reduces transpiration and improves water‐use efficiency (WUE) (Wang et al ., 2016; Kelly et al ., 2019). Thus, NO and H 2 O 2 participate extensively in a plant’s tolerance of drought (Santisree et al ., 2015; Fancy et al ., 2017; X. Wang et al ., 2020).…”

Soybean Root Growth in Response to Chemical, Physical, and Biological Soil Variations

“…Water is absorbed by the roots, so providing adequate conditions for radicial growth, in volume and depth, can be an alternative to decrease the stress caused by the lack of water; thus, the roots will explore greater soil volume, consequently, will be in contact with a higher volume of water. The lack of water to the plants causes the closure of the stomata and decreases the plants' photosynthetic rate, causing losses in soybean grain production (Zhang et al, 2016;Kelly et al, 2019).…”