Abstract
In plants, resistance proteins are immune receptors that upon pathogen recognition trigger a signal transduction cascade leading to a rapid defence response. The nucleotide-binding and leucine-rich repeat (NB-LRR) proteins form the major class of immune receptors. The potato NB-LRR Rx confers
resistance to potato virus X (PVX) by recognition of the viral coat protein. Rx localises to the cytoplasm, but it was recently shown to also accumulate in the nucleus, despite the absence of a discernible nuclear localisation signal (NLS). In the cytoplasm Rx associates with a RanGTPase-activating protein 2 (RanGAP2), which is required for resistance to PVX (Tameling and Baulcombe, 2007, Plant Cell; Sacco et al., 2007, Plant J). RanGAPs are highly conserved in eukaryotes
and are required for the regulation of nucleo-cytoplasmic trafficking of macromolecules (e.g. proteins) through the nuclear pores. Co-expression studies in Nicotiana benthamiana revealed that overexpression of RanGAP2 (in the cytoplasm) attenuates the nuclear accumulation of Rx, and largely
potentiates the weak autoactive phenotype of a truncated Rx protein. The inverse was observed when the WPP-domain of RanGAP2, which mediates interaction with Rx, was forced to accumulate in the nucleus by fusion with an NLS. Hence, co-expressed Rx hyper accumulated in the nucleus, which
coincided with an abolishment of the autoactivity of several Rx mutants. Our data suggest that the ratio between the Rx pool in the cytoplasm and in the nucleoplasm dictates the initiation of defence signalling, possibly via influencing the compartimentalisation of a transcriptional regulator. Further studies will focus on whether such dynamic changes in Rx localisation indeed also occur upon PVX infection and are actually responsible for mediating PVX resistance.
resistance to potato virus X (PVX) by recognition of the viral coat protein. Rx localises to the cytoplasm, but it was recently shown to also accumulate in the nucleus, despite the absence of a discernible nuclear localisation signal (NLS). In the cytoplasm Rx associates with a RanGTPase-activating protein 2 (RanGAP2), which is required for resistance to PVX (Tameling and Baulcombe, 2007, Plant Cell; Sacco et al., 2007, Plant J). RanGAPs are highly conserved in eukaryotes
and are required for the regulation of nucleo-cytoplasmic trafficking of macromolecules (e.g. proteins) through the nuclear pores. Co-expression studies in Nicotiana benthamiana revealed that overexpression of RanGAP2 (in the cytoplasm) attenuates the nuclear accumulation of Rx, and largely
potentiates the weak autoactive phenotype of a truncated Rx protein. The inverse was observed when the WPP-domain of RanGAP2, which mediates interaction with Rx, was forced to accumulate in the nucleus by fusion with an NLS. Hence, co-expressed Rx hyper accumulated in the nucleus, which
coincided with an abolishment of the autoactivity of several Rx mutants. Our data suggest that the ratio between the Rx pool in the cytoplasm and in the nucleoplasm dictates the initiation of defence signalling, possibly via influencing the compartimentalisation of a transcriptional regulator. Further studies will focus on whether such dynamic changes in Rx localisation indeed also occur upon PVX infection and are actually responsible for mediating PVX resistance.
| Original language | English |
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| Title of host publication | ISMPMI International Congress abstracts, Quebec City, Canada, 19-23 July 2009 |
| Place of Publication | Quebec |
| Publisher | MPMI |
| Publication status | Published - 2009 |
| Event | XIV International Congress on Molecular Plant-Microbe Interactions, Quebec City, Canada - Duration: 19 Jul 2009 → 23 Jul 2009 |
Conference/symposium
| Conference/symposium | XIV International Congress on Molecular Plant-Microbe Interactions, Quebec City, Canada |
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| Period | 19/07/09 → 23/07/09 |