Key message
Importance of the UPR for pollen.
Abstract
Pollen is particularly sensitive to environmental conditions that disturb protein homeostasis, such as higher temperatures. Their survival is dependent on subcellular stress response systems, one of which maintains protein homeostasis in the endoplasmic reticulum (ER). Disturbance of ER proteostasis due to stress leads to the activation of the unfolded protein response (UPR) that mitigates stress damage mainly by increasing ER-folding capacity and reducing folding demands. The UPR is controlled by ER membrane-associated transcription factors and an RNA splicing factor. They are important components of abiotic stress responses including general heat stress response and thermotolerance. In addition to responding to environmental stresses, the UPR is implicated in developmental processes required for successful male gametophyte development and fertilization. Consequently, defects in the UPR can lead to pollen abortion and male sterility. Several UPR components are involved in the elaboration of the ER network, which is required for pollen germination and polar tube growth. Transcriptome and proteome analyses have shown that components of the ER-folding machinery and the UPR are upregulated at specific stages of pollen development supporting elevated demands for secretion. Furthermore, genetic studies have revealed that knockout mutants of UPR genes are defective in producing viable or competitive pollen. In this review, we discuss recent findings regarding the importance of the UPR for both pollen development and stress response.
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Acknowledgments
The authors would like to thank Klaus-Dieter Scharf for helpful comments and SPOT-ITN consortium for the support. The work is supported by SPOT-ITN/Marie-Curie to ES and the China Scholarship Council to YH.
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Communicated by David Twell.
A contribution to the special issue ‘Pollen development and stress response’.
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Supplementary Table 1
Expression of Arabidopsis thaliana genes induced by tunicamycin treatment, during pollen development. The 193 genes were selected from three studies (Iwata et al. 2010; Martínez and Chrispeels 2003; Sugio et al. 2009). The expression data derive from the studies of Honys and Twell (2004) for development and Qin et al. (2009) for germination, and values were obtained from The Pollen Transcriptome Navigator (http://pollen.umd.edu/). For relative expression, the expression values were normalized against UN or DP samples (XLS 3222 kb)
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Fragkostefanakis, S., Mesihovic, A., Hu, Y. et al. Unfolded protein response in pollen development and heat stress tolerance. Plant Reprod 29, 81–91 (2016). https://doi.org/10.1007/s00497-016-0276-8
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DOI: https://doi.org/10.1007/s00497-016-0276-8