Aquaporins in developing rice grains.

Hidehiro Hayashi,Mari Murai-Hatano,Matsuo Uemura,Junko Ishikawa-Sakurai,Arifa Ahamed

doi:10.1080/09168451.2015.1032882

Hidehiro Hayashi, Mari Murai-Hatano + Show 3 more

Open Access

https://doi.org/10.1080/09168451.2015.1032882

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Abstract

During rice grain filling, grain moisture content and weight show dynamic changes. We focused on the expression of all 33 rice aquaporins in developing grains. Only two aquaporin genes, OsPIP2;1 and OsTIP3;1, were highly expressed in the period 10-25 days after heading (DAH). High-temperature treatment from 7 to 21 DAH abolished the dynamic up-regulation of OsPIP2;1 in the period 15-20 DAH, whereas OsTIP3;1 expression was not affected. Immunohistochemical analysis revealed that OsPIP2;1 was present in the starchy endosperm, nucellar projection, nucellar epidermis, and dorsal vascular bundles, but not in the aleurone layer. OsTIP3;1 was present in the aleurone layer and starchy endosperm. Water transport activity of recombinant OsTIP3;1 was low, in contrast to the high activity of recombinant OsPIP2;1 we reported previously. Our data suggest that OsPIP2;1 and OsTIP3;1 have distinct roles in developing grains.

Highlights

IntroductionGrain moisture content and weight show dynamic changes. We focused on the expression of all 33 rice aquaporins in developing grains
During rice grain filling, grain moisture content and weight show dynamic changes
It has been proposed that xylem vessels in dorsal vascular bundles function as drain pipes to maintain low turgor pressure in the phloem.2–4) no transpiration stream from the roots has been observed in the xylem in dorsal vascular bundles,4,5) and the transpiration rate from rice grains is related to grain dry matter increase.6) the mechanism of efficient control of water flow from the phloem to the xylem vessels in the dorsal vascular bundles is unclear

Summary

Introduction

Grain moisture content and weight show dynamic changes. We focused on the expression of all 33 rice aquaporins in developing grains. Grain moisture content and weight change dynamically as a result of the transport of large amounts of assimilates; this transport is linked to water movement in developing grains. The pathways for transporting assimilates and water into the developing grain were proposed.3,7–9) After aleurone layer differentiation (6–7 days after anthesis),10) these pathways have to through the aleurone layer.11) the aleurone layer may play important roles in water and solute transport. All of these processes might be mediated by water channels (aquaporins) and solute channels, but the relation between grain development and aquaporins remains largely unexplored. Absolute mRNA copy numbers per pg of total RNA were calculated using standard plasmids carrying each aquaporin cDNA as reported by Sakurai-Ishikawa et al.16)

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