Abstract
BackgroundThe antioxidant glutathione fulfills many important roles during plant development, growth and defense in the sporophyte, however the role of this important molecule in the gametophyte generation is largely unclear. Bioinformatic data indicate that critical control enzymes are negligibly transcribed in pollen and sperm cells. Therefore, we decided to investigate the role of glutathione synthesis for pollen germination in vitro in Arabidopsis thaliana accession Col-0 and in the glutathione deficient mutant pad2-1 and link it with glutathione status on the subcellular level.ResultsThe depletion of glutathione by buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, reduced pollen germination rates to 2-5% compared to 71% germination in wildtype controls. The application of reduced glutathione (GSH), together with BSO, restored pollen germination and glutathione contents to control values, demonstrating that inhibition of glutathione synthesis is responsible for the decrease of pollen germination in vitro. The addition of indole-3-acetic acid (IAA) to media containing BSO restored pollen germination to control values, which demonstrated that glutathione depletion in pollen grains triggered disturbances in auxin metabolism which led to inhibition of pollen germination.ConclusionsThis study demonstrates that glutathione synthesis is essential for pollen germination in vitro and that glutathione depletion and auxin metabolism are linked in pollen germination and early elongation of the pollen tube, as IAA addition rescues glutathione deficient pollen.
Highlights
The antioxidant glutathione fulfills many important roles during plant development, growth and defense in the sporophyte, the role of this important molecule in the gametophyte generation is largely unclear
Pollen germination Wildtype pollen grains showed a germination rate of 71% when grown on germination medium without reduced glutathione (GSH) and buthionine sulfoximine (BSO) (Figure 1 and Figure 2)
To examine whether glutathione depletion may be linked with decreased levels of auxin, which is one of the most important plant hormones for pollen tube growth [33,34], we have applied 22.8 μM indole-3-acetic acid (IAA) together with BSO in the growth media
Summary
The antioxidant glutathione fulfills many important roles during plant development, growth and defense in the sporophyte, the role of this important molecule in the gametophyte generation is largely unclear. Glutathione is an important antioxidant and redox buffer in eukaryotes and most prokaryotes that fulfills many roles in plant metabolism and plant defense during abiotic and biotic stress conditions in the sporophyte [1], but its role remains largely unknown for the gametophyte. Bioinformatic data cast doubt on the importance of glutathione metabolism in the male gametophyte, as both GSH1 and GSH2 are transcribed at negligible levels in pollen and sperm cells (Additional files 1 and 2) [23,24]. Due to the apparent sensitivity of microspores to mitochondrial damage induced by chronic oxidative stress [25], we decided to investigate the necessity and localization of glutathione in the gametophyte in order to reveal strategies for pollen to cope with ROS during tube germination and elongation
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