Abstract
Cytidine triphosphate synthase (CTPS) catalyzes the final step in pyrimidine de novo synthesis. In Arabidopsis, this protein family consists of five members (CTPS1–5), and all of them localize to the cytosol. Specifically, CTPS4 showed a massive upregulation of transcript levels during abiotic stress, in line with increased staining of CTPS4 promoter:GUS lines in hypocotyl, root and to lesser extend leaf tissues. In a setup to study progressive drought stress, CTPS4 knockout mutants accumulated less fresh and dry weight at days 5–7 and showed impaired ability to recover from this stress after 3 days of rewatering. Surprisingly, a thorough physiological characterization of corresponding plants only revealed alterations in assimilation and accumulation of soluble sugars including those related to drought stress in the mutant. Bimolecular fluorescence complementation (BiFC) studies indicated the interaction of CTPS4 with other isoforms, possibly affecting cytoophidia (filaments formed by CTPS formation. Although the function of these structures has not been thoroughly investigated in plants, altered enzyme activity and effects on cell structure are reported in other organisms. CTPS activity is required for cell cycle progression and growth. Furthermore, drought can lead to the accumulation of reactive oxygen species (ROS) and by this, to DNA damage. We hypothesize that effects on the cell cycle or DNA repair might be relevant for the observed impaired reduced drought stress tolerance of CTPS4 mutants.
Highlights
IntroductionDrought and salt stress lead to large losses in plant growth and productivity
Due to climate change, plants are facing ever-increasing challenges
It was apparent that CTPS4 (At4g20320) expression was strongly increased upon drought and salt stress (Hruz et al, 2008; Zhang et al, 2008)
Summary
Drought and salt stress lead to large losses in plant growth and productivity. An adequate water supply is essential for regulated growth, whereas periods of drought lead to major changes in metabolism as it represents a stress situation for them (Bray, 2004). Thereby, plants naturally sense and respond to water stress by activating specific signaling pathways leading to physiological and developmental adaptations. The detection of drought basically takes place through two different signaling pathways. The abscisic acid (ABA)-dependent pathway is activated in the early acclimation phase (Verslues and Bray, 2006; Singh and Laxmi, 2015). ABA receptors inhibit the activity of protein
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