Role of Aquaporins in Plant Water Balance

Sulthan Ramiz

PGIS/SED/14/02

PGIS

Contents

Introductions

What are aquaporins?

Structure of Aquaporins

Aquaporins in plants and their role

Conclusions

Bibliography

Introduction

http://journal.frontiersin.org/Journal/10.3389/fpls.2014.00224/

full

What are Aquaporins?

Specialized protein located in the cell membrane of cells.

Aquaporins are part of the large family of major intrinsic

proteins, proteins that form pores or channels in the cell

membrane, and work to regulate the composition of the inside

of the cell.

It forms the mechanism responsible for pumping water into and

out of the cell as needed.

Some aquaprorins can conduct carbon dioxide

How does APs look like?

(Gonen,T, & Walz,T, 2006: http://cryoem.janelia.org/uploads/image/pdfs/gonenwalz_2006.pdf)

Aps in Plants & their role • Higher number of aquaporins compared to mammals.

Aps in Plants

Plasma membrane

intrinsic proteins, PIPs

PIP1

PIP2

Tonoplast intrinsic

proteins, TIPs

NOD26-like intrinsic

proteins, NLMs, NIPs

Small basic intrinsic

proteins, SIPs

Aps and root water uptake Many aquaporins are know to be expressed in roots.

Tomato Tobacco Arabidopsis0

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Percentage reduction in hydraulic conductance in three species of plants due to inhibition of aquaporins in root

Species of plant

% re

ducti

on h

ydra

ulic

con

duct

ance

APS and xylem water transport No direct involvement of APs on water transport in xylem. The surrounding cells contribute to the regulation of xylem

transport. In roots and leaves, Apoplastic water pathways compete with

transcellular, aquaporin-controlled water pathways indirect control mechanism of xylem water flow which depends on the Aps function.

http://www.studyblue.com/notes/note/n/exam-1/deck/2057463

APS mediated water balance at the interface between xylem and its surrounding cells cauliflowers drying of floret tissues slices cell volume reduction expression of Aps in affected & differentiated cells, water xylem.

This provides a tool to explain unclear mechanism of plant xylem recovery from water deficit.

APS and xylem water transport

Loss

of c

ondu

ctan

ce (

%)

Aquaporins and water stress Actually, the responses of aquaporins to water stress may involve

either up- or down-regulation of gene expression or no change depending on the time course and intensity of water stress.

Drought adapted & non adapted verities affect Aps expression.

Regulation of photosynthesis

Mesophyll conductanc

e to CO2

Stomata control

Water balance

Leafy hydraulic conductance

Aquaporins could be involved in the regulation of leaf hydraulic conductivity, although direct evidence is scarce.

more physiological studies using aquaporin knockouts would be needed to establish the role that aquaporins play in the regulation of leaf hydraulic conductivity