scholarly journals Out of the blue; Phototropins of the leaf vascular bundle sheath mediate the blue light regulation of the leaf hydraulic conductance

2019 ◽  
Author(s):  
Yael Grunwald ◽  
Sanbon Chaka Gosa ◽  
Tanmayee Torne ◽  
Nava Moran ◽  
Menachem Moshelion
Keyword(s):  
Signal Transduction ◽  
Blue Light ◽  
Vascular Bundle ◽  
Vascular Tissue ◽  
Xylem Sap ◽  
Signal Transduction Pathway ◽  
Hydraulic Conductance ◽  
Bundle Sheath ◽  
Transduction Pathway ◽  
Water Permeability Coefficient

ABSTRACTThe leaf vascular bundle sheath cells (BSCs), which tightly envelop the leaf veins, constitute a selective dynamic barrier to water and solutes radially entering the mesophyll and play a major role in regulating the leaf radial hydraulic conductance (Kleaf). Recently, we showed that the BSCs’ plasma membrane H+-ATPase, AHA2, increases Kleaf by acidifying the xylem sap. Since BL reportedly increases Kleaf and we found the blue light (BL) receptor genes, PHOT1 and PHOT2 expressed in the Arabidopsis BSCs, we hypothesized that, similar to the guard cells (GCs) BL signal transduction pathway, the BSCs’ PHOT1 and PHOT2 activate the BSCs’ H+-ATPase and thus regulate Kleaf. Indeed, under BL illumination, the Kleaf in the knockout mutant lines phot1-5, phot2-1, phot1-5phot2-1 and aha2-4 was lower than in WT. BSCs-directed complementation (using the SCR promoter) of phot1-5 and aha2-4 respectively by PHOT1 and AHA2, restored the BL-induced Kleaf increase. BSCs-specific silencing of PHOT1 or PHOT2 (using the SCR promoter) abolished the BL-induced Kleaf increase. Xylem-fed PHOT inhibitor, tyrphostin 9, also abolished the BL-induced Kleaf increase in WT. Moreover, in WT plants, white light (WL) acidified the xylem sap compared to dark, but did not acidify the xylem sap of the phot1-5 mutant. BSCs-specific complementation of phot1-5 by SCR: PHOT1, restored the WL-induced xylem acidification. On a cellular level, BL hyperpolarized the BSCs, which was prevented by tyrphostin 9. In addition, the osmotic water permeability coefficient (Pf) of the BSCs was higher under WL treatment. Our results link the blue light control of water fluxes from the xylem to the mesophyll via the BSCs in the following model:BL →BSCs’ PHOTs activation →tyrosine phosphorylation→BSCs’ H+- ATPase activation →BSCs hyperpolarization, xylem acidification →Pf elevation → Kleaf increase. Thus, this study is the first to demonstrate an independent BL signal transduction pathway regulation of the vascular tissue.

The blue light signal transduction pathway is involved in anthocyanin accumulation in ‘Red Zaosu’ pear

Planta ◽  
2018 ◽  
Vol 248 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Ruiyan Tao ◽  
Songling Bai ◽  
Junbei Ni ◽  
Qinsong Yang ◽  
Yuan Zhao ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Blue Light ◽  
Signal Transduction Pathway ◽  
Light Signal ◽  
Transduction Pathway ◽  
Anthocyanin Accumulation ◽  
Light Signal Transduction

scholarly journals Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+-ATPase of vascular bundle sheath cells

2017 ◽  
Author(s):  
Yael Grunwald ◽  
Noa Wigoda ◽  
Nir Sade ◽  
Adi Yaaran ◽  
Tanmayee Torne ◽  
...  
Keyword(s):  
Proton Pump ◽  
Vascular Bundle ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Bundle Sheath ◽  
List Type ◽  
Mesophyll Cells ◽  
Leaf Hydraulic Conductance ◽  
Bundle Sheath Cells ◽  
Sheath Cells

AbstractThe leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem-sap pH of <6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates this pH and leaf radial water fluxes.We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts.Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf.All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance.One-sentence summaryBundle-sheath cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH

Dissecting blue light signal transduction pathway in leaf epidermis using a pharmacological approach

Planta ◽  
2015 ◽  
Vol 242 (4) ◽  
pp. 813-827 ◽  
Author(s):  
Branka D. Živanović ◽  
Lana I. Shabala ◽  
Theo J. M. Elzenga ◽  
Sergey N. Shabala
Keyword(s):  
Signal Transduction ◽  
Blue Light ◽  
Signal Transduction Pathway ◽  
Light Signal ◽  
Transduction Pathway ◽  
Leaf Epidermis ◽  
Light Signal Transduction ◽  
Pharmacological Approach

Kinetic analysis of a signal-transduction pathway by time-resolved somatic complementation of mutants.

1998 ◽  
Vol 201 (13) ◽  
pp. 1991-1999 ◽  
Author(s):  
C Starostzik ◽  
W Marwan
Keyword(s):  
Signal Transduction ◽  
Blue Light ◽  
Red Light ◽  
Signal Transduction Pathway ◽  
Intermediate Phenotype ◽  
Regulatory Function ◽  
Transduction Pathway ◽  
Wild Type ◽  
Time Resolved ◽  
Small Change

Sensory control of sporulation in Physarum polycephalum plasmodia is mediated by a branched signal-transduction pathway that integrates blue light, far-red light, heat shock and the starvation state. Mutants defective in the pathway were isolated and three phenotypes obtained: blue-blind, general-blind and light-independent sporulating. When plasmodia of the blue-blind mutant Blu1 were exposed to a pulse of blue light and subsequently fused to non-induced wild-type plasmodia, the resulting heterokaryons sporulated, indicating a functional blue- light photoreceptor in the mutant. When the general-blind mutant Nos1 was fused to a wild-type plasmodium which had been induced by light, sporulation of the heterokaryon was blocked. However, the dominant inhibition of sporulation by Nos1 was gradually lost with increasing time between induction by light and time of fusion, suggesting that Nos1 can be bypassed by the time-dependent formation of a downstream signal-transduction intermediate. Phenotype expression in constitutively sporulating (Cos) mutants depended on starvation. The Cos2 product was titrated by fusing mutant plasmodia of different sizes to wild-type plasmodia of constant size and analysing the sporulation probability of the resulting heterokaryon. The titration curve indicates that a small change in the amount of Cos2 product can cause sporulation. We conclude that somatic complementation analysis allows the time-resolved evaluation of the regulatory function of mutations in a signal-transduction pathway without prior cloning of the gene. This shortcut allows us to characterize many mutants quickly and to select those for molecular analysis that display a well-defined regulatory function.

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