Ectopic expression of S-RNase of Petunia inflata in pollen results in its sequestration and non-cytotoxic function

Xiaoying Meng, Zhihua Hua, Ning Wang, Allison M. Fields, Peter E. Dowd, Teh hui Kao

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The specificity of S-RNase-based self-incompatibility (SI) is controlled by two S-locus genes, the pistil S-RNase gene and the pollen S-locus-F-box gene. S-RNase is synthesized in the transmitting cell; its signal peptide is cleaved off during secretion into the transmitting tract; and the mature "S-RNase", the subject of this study, is taken up by growing pollen tubes via an as-yet unknown mechanism. Upon uptake, S-RNase is sequestered in a vacuolar compartment in both non-self (compatible) and self (incompatible) pollen tubes, and the subsequent disruption of this compartment in incompatible pollen tubes correlates with the onset of the SI response. How the S-RNase-containing compartment is specifically disrupted in incompatible pollen tubes, however, is unknown. Here, we circumvented the uptake step of S-RNase by directly expressing S2-RNase, S3-RNase and non-glycosylated S3-RNase of Petunia inflata, with green fluorescent protein (GFP) fused at the C-terminus of each protein, in self (incompatible) and non-self (compatible) pollen of transgenic plants. We found that none of these ectopically expressed S-RNases affected the viability or the SI behavior of their self or non-self-pollen/pollen tubes. Based on GFP fluorescence of in vitro-germinated pollen tubes, all were sequestered in both self and non-self-pollen tubes. Moreover, the S-RNase-containing compartment was dynamic in living pollen tubes, with movement dependent on the actin-myosin-based molecular motor system. All these results suggest that glycosylation is not required for sequestration of S-RNase expressed in pollen tubes, and that the cytosol of pollen is the site of the cytotoxic action of S-RNase in SI.

Original languageEnglish (US)
Pages (from-to)263-275
Number of pages13
JournalSexual Plant Reproduction
Volume22
Issue number4
DOIs
StatePublished - Nov 2009

All Science Journal Classification (ASJC) codes

  • Plant Science
  • Cell Biology

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