Physiologically active stomatal control originated at least as far back as the emergence of the lycophytes

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Figure 4. Stomatal Response Mechanisms Are Conserved between a Basal Vascular Plant and Flowering Plants (A) Treatment with the Ca2+ chelator EGTA (+EGTA, 10 mM) or the Ca2+ channel blocker verapamil (+Ver, 25 μM) partially inhibits ABA-induced reductions in S. uncinata stomatal aperture. Gray bars show controls, white bars show 25 μM ABA. Data are mean values ± SEM of three independent experiments (n = 120). Stomata are significantly more closed with ABA alone than in combination with EGTA or verapamil (p < 0.005; Student’s t test). (B) Following ABA treatment (white bar, 25 μM ABA), reactive oxygen species (ROS) levels in S. uncinata stomata increase significantly compared to controls (gray bar, −ABA) (p < 0.005; Student’s t test) as detected by fluorescence intensity of H2DCF-DA. Data shown are mean fluorescence intensity ± SEM of three independent experiments (n = 150). (C and D) Accumulation of vacuolar K+ deposits in guard cells of S. uncinata incubated in light (C) or dark (D) conditions. White arrows highlight sodium potassium cobaltinitrite deposit (n = 3). (E) 10 μM fusicoccin (FC, hatched bar) promotes significant stomatal opening in preclosed stomata of S. uncinata compared to control (black bar) (p < 0.005; Student’s t test). Data shown are mean values ± SEM from three independent experiments (n = 100). (F) ABA-induced promotion of stomatal closure in Arabidopsis thaliana lines wild-type (WT; Col-2), ost1-4, and three T2 independent transgenic lines (#1–#3) expressing SmOST1 in the ost1-4 background (ost1-4;AtOST1PRO::SmOST1). Transgenic lines are indicated by brackets. Data are mean values ± SEM (n = 90) for peels incubated with 1 μM ABA (light gray bars) and 10 μM ABA (white bars) or controls (dark gray bars); ABA induces significant closure in the WT line and transgenic lines #1, #2, and #3 (p < 0.001; Student’s t test). ABA and control treatments do not differ significantly in ost1-4 (p = 0.125; Student’s t test). (G) Detection of the SmOST1 transgene in complemented lines #1, #2, and #3 by RT-PCR. Actin was amplified as a control. Transgenic lines expressing SmOST1 in the ost1-4 background (ost1-4;AtOST1PRO::SmOST1) are indicated by the bracket.

 

Land plants acquired active stomatal control early in their evolutionary history

by Ruszala E. M., Beerling D. J., Franks P. J., Chater C., Casson S. A., Gray J. E., Hetherington A. M. (2011)

Elizabeth M.Ruszala, David J.Beerling, Peter J.Franks, 2CasparChater, Stuart A.Casson, Julie E.Gray, Alistair M.Hetherington, 1

1
School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK
2
Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
3
Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
4
Faculty of Agriculture, Food & Natural Resources, The University of Sydney, Sydney, NSW 2006, Australia

===

in Curr Biol 21(12): 1030–1035 – https://doi.org/10.1016/j.cub.2011.04.044 –

https://www.sciencedirect.com/science/article/pii/S0960982211004866

Summary

Stomata are pores that regulate plant gas exchange [1]. They evolved more than 400 million years ago [23], but the origin of their active physiological responses to endogenous and environmental cues is unclear [23456]. Recent research suggests that the stomata of lycophytes and ferns lack pore closure responses to abscisic acid (ABA) and CO2. This evidence led to the hypothesis that a fundamental transition from passive to active control of plant water balance occurred after the divergence of ferns 360 million years ago [78]. Here we show that stomatal responses of the lycophyte Selaginella [9] to ABA and CO2 are directly comparable to those of the flowering plant Arabidopsis [10]. Furthermore, we show that the underlying intracellular signaling pathways responsible for stomatal aperture control are similar in both basal and modern vascular plant lineages. Our evidence challenges the hypothesis that acquisition of active stomatal control of plant carbon and water balance represents a critical turning point in land plant evolution [78]. Instead, we suggest that the critical evolutionary development is represented by the innovation of stomata themselves and that physiologically active stomatal control originated at least as far back as the emergence of the lycophytes (circa 420 million years ago) [11].

Highlights

► Active stomatal responses to CO2 and ABA are evolutionarily ancient

► Active stomatal responses to CO2 and ABA are present in Selaginella

► Stomata are a key evolutionary innovation vital to the success of the land plants

Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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