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Open Access Research article

Glycoprotein composition along the pistil of Malus x domestica and the modulation of pollen tube growth

Juan M Losada12 and Maria Herrero1*

Author Affiliations

1 Pomology Department, Aula Dei Experimental Station CSIC, Apdo 13034, 50080 Zaragoza, Spain

2 Present address: Arnold Arboretum of Harvard University, 1300 Centre Street, 02131 Boston, MA, USA

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BMC Plant Biology 2014, 14:1  doi:10.1186/1471-2229-14-1

Published: 3 January 2014

Abstract

Background

The characteristics of pollen tube growth are not constant, but display distinct patterns of growth within the different tissues of the pistil. In the stigma, the growth rate is slow and autotrophic, whereas in the style, it is rapid and heterotrophic. Very little is known about the interactions between these distinct maternal tissues and the traversing pollen tube and the role of this interaction on the observed metabolism. In this work we characterise pollen tube growth in the apple flower and look for differences in glycoprotein epitope localization between two different maternal tissues, the stigma and the style.

Results

While immunocytochemically-detected arabinogalactan proteins were present at high levels in the stigma, they were not detected in the transmitting tissue of the style, where extensins were abundant. Whereas extensins remained at high levels in unpollinated pistils, they were no longer present in the style following pollen tube passage. Similarily, while abundant in unpollinated styles, insoluble polysaccharides such as β-glucans, were depleted in pollinated pistils.

Conclusions

The switch from autotropic to heterotrophic pollen tube growth correlates spatially with a change of glycoprotein epitopes between the stigma and the style. The depletion of extensins and polysaccharides following pollen tube passage in the style suggest a possible contribution to the acceleration of heterotrophic pollen tube growth, which would imply an active contribution of female tissues on prezygotic male–female crosstalk.

Keywords:
Arabinogalactan proteins; AGPs; Apple; Callose; Extensins; EXTs; Malus x domestica; Pistil; Pollen tube; Style; Transmitting tissue