© 2008 The Author(s).
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RESEARCH PAPER |
IAA stimulates pollen tube growth and mediates the modification of its wall composition and structure in Torenia fournieri
1Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
2College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, China
* To whom correspondence should be addressed. E-mail: jzhao{at}whu.edu.cn
The effects of several hormones on pollen tube growth were compared in Torenia fournieri and it was found that IAA was the most effective, stimulating pollen tube growth and causing the shank part of pollen tubes to be slender and straighter. The role of IAA was investigated by studying the changes in ultrastructure and PM H+-ATPase distribution in the pollen tubes and the modification of the tube wall. Using the fluorescent marker FM4-64, together with transmission electron microscopy, it was shown that secretory vesicles and mitochondria increased in IAA-treated tubes. Immunolocalization and fluorescence labelling, together with Fourier-transform infrared analysis, detected that IAA enhanced the level of PM H+-ATPase and the synthesis of pectins, and reduced the cellulose density in pollen tubes. Importantly, to observe the orientation of cellulose microfibrils in pollen tubes in situ, atomic force microscopy was used to examine the ‘intact’ tube wall. Atomic force microscopy images showed that cellulose microfibrils were parallel to each other in the subapical region of IAA-treated tubes, but disorganized in control tubes. All results provided new insights into the functions of cellulose microfibrils in pollen tube growth and direction, and revealed that the IAA-induced changes of pollen tubes were attributed to the increase in secretory vesicles, mitochondria, and PM H+-ATPase, and the modification of pectin and cellulose microfibrils in the tube wall.
Key words: AFM, cellulose microfibrils, FTIR, IAA, PM H+-ATPase, pollen tube, secretory vesicles, Torenia fournieri
Received 24 January 2008; Revised 27 March 2008 Accepted 31 March 2008
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