Postmeiotic development of pollen surface layers requires two Arabidopsis ABCG-type transporters
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Two Arabidopsis ABC transporters, ABCG1 and ABCG16, are expressed in the tapetal layer, specifically after postmeiotic microspore release, and play important roles in pollen surface development.
The male gametophytic cells of terrestrial plants, the pollen grains, travel far before fertilization, and thus require strong protective layers, which take the form of a pollen coat and a pollen wall. The protective surface structures are generated by the tapetum, the tissue surrounding the developing gametophytes. Many ABC transporters, including Arabidopsis thaliana ABCG1 and ABCG16, have been shown to play essential roles in the development of such protective layers. However, the details of the mechanism of their function remain to be clarified. In this study, we show that ABCG1 and ABCG16 are localized at the plasma membrane of tapetal cells, specifically after postmeiotic microspore release, and play critical roles in the postmeiotic stages of male gametophyte development. Consistent with this stage-specific expression, the abcg1 abcg16 double knockout mutant exhibited defects in pollen development after postmeiotic microspore release; their microspores lacked intact nexine and intine layers, exhibited defects in pollen mitosis I, displayed ectopic deposits of arabinogalactan proteins, failed to complete cytokinesis, and lacked sperm cells. Interestingly, the double mutant exhibited abnormalities in the internal structures of tapetal cells, too; the storage organelles of tapetal cells, tapetosomes and elaioplasts, were morphologically altered. Thus, this work reveals that the lack of ABCG1 and ABCG16 at the tapetal cell membrane causes a broad range of defects in pollen, as well as in tapetal cells themselves. Furthermore, these results suggest that normal pollen surface development is necessary for normal development of the pollen cytoplasm.
KeywordsPollen surface ABC transporter Postmeiotic development Tapetosome Elaioplast
- ABC transporter
ATP-binding cassette transporter
Transposable element silencing via AT-hook
Transmission electron microscopy
This work was supported by the National Research Foundation (NRF) of Korea Grant funded by the Ministry of Science, Information and Communication Technology, and Future Planning, Korea awarded to Y.L. (NRF-2015R1A2A1A01004294), Grants from the National Key Basic Research Developments Program, Ministry of Science and Technology, China (2013CB126902); National Transgenic Major Program (2016ZX08009003-003-007) awarded to D. Zhang, and by the Direct Grant for Research from the Chinese University of Hong Kong (4053089 and 3132797) to B. Kang.
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Conflict of interest
The authors declare no conflict of interest.
- Choi H, Ohyama K, Kim YY, Jin JY, Lee SB, Yamaoka Y, Muranaka T, Suh MC, Fujioka S, Lee Y (2014) The role of Arabidopsis ABCG9 and ABCG31 ATP binding cassette transporters in pollen fitness and the deposition of steryl glycosides on the pollen coat. Plant Cell Online 26:310–324CrossRefGoogle Scholar
- Scott R (1994) Pollen exine-the sporopollenin enigma and the physics of pattern. In: SEMINAR SERIES-SOCIETY FOR EXPERIMENTAL BIOLOGY. Cambridge University Press, pp 49–49Google Scholar
- Wellman CH (2004) Origin, function and development of the spore wall in early land plants. Evolut Plant Physiol 21Google Scholar