Downregulation of the auxin transporter gene SlPIN8 results in pollen abortion in tomato
SlPIN8 is expressed specifically within tomato pollen, and that it is involved in tomato pollen development and intracellular auxin homeostasis.
The auxin (IAA) transport protein PIN-FORMED (PIN) plays key roles in various aspects of plant development. The biological role of the auxin transporter SlPIN8 in tomato development remains unclear. Here, we examined the expression pattern of the SlPIN8 gene in vegetative and reproductive organs of tomato. RNA interference (RNAi) transgenic lines specifically silenced for the SlPIN8 gene were generated to identify the role of SlPIN8 in pollen development. We found that SlPIN8 mRNA is expressed specifically within tomato pollen. In the anthers, the highest mRNA expression and β-glucuronidase (GUS) activity of promoter-SlPIN8-GUS was detected during late stages of anther development, when pollen maturation occurred. The downregulation of SlPIN8 did not drastically affect the vegetative growth of tomato. However, in SlPIN8-RNAi transgenic plants, approximately 80% of the pollen grains were identified to be abnormal and lack viability; they were shriveled and flattened. Furthermore, the downregulation of SlPIN8 affected the gene expression of some anther development-specific proteins. SlPIN8-RNAi transgenic plants induced seedless fruits because of defective pollen function rather than defective female gametophyte function. In addition, SlPIN8 was found to localize to the endoplasmic reticulum, consistent with the changes in the auxin levels of SlPIN8-RNAi lines, whereas the level of free IAA was increased in SlPIN8-overexpressing protoplasts, indicating that SlPIN8 is involved in intracellular auxin homeostasis.
KeywordsAuxin SlPIN8 Pollen RNAi Endoplasmic reticulum
This work was supported by the Modern Agricultural Industry Technology System (CARS-27); Special Fund for Agro-Scientific Research in the Public Interest (201203075); Key Laboratory of Biology and Genetic Improvement of Horticultural Crop (Nutrition and Physiology) in Ministry of Agriculture, and Key Laboratory of Stress Physiology and Molecular Biology for Fruit Trees in Beijing Municipality.
ZG designed and conducted the experiments, analyzed the data, accomplished pictures and wrote the manuscript. YF, YW, TW, XX contributed in design of the experiments. XZ designed the experiments and finalized the manuscript. ZH conceived and designed the experiments, and finalized the manuscript. All authors read and approved the final manuscript.
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