NaStEP: A Proteinase Inhibitor Essential to Self-Incompatibility and a Positive Regulator of HT-B Stability in Nicotiana alata Pollen Tubes
Por:
Jiménez-Durán K., McClure B., García-Campusano F., Rodríguez-Sotres R., Cisneros J., Busot G., Cruz-García F.
Publicada:
1 ene 2013
Resumen:
In Solanaceae, the self-incompatibility S-RNase and S-locus F-box
interactions define self-pollen recognition and rejection in an
S-specific manner. This interaction triggers a cascade of events
involving other gene products unlinked to the S-locus that are crucial
to the self-incompatibility response. To date, two essential
pistil-modifier genes, 120K and High Top-Band (HT-B), have been
identified in Nicotiana species. However, biochemistry and genetics
indicate that additional modifier genes are required. We recently
reported a Kunitz-type proteinase inhibitor, named NaStEP (for Nicotiana
alata Stigma-Expressed Protein), that is highly expressed in the stigmas
of self-incompatible Nicotiana species. Here, we report the proteinase
inhibitor activity of NaStEP. NaStEP is taken up by both compatible and
incompatible pollen tubes, but its suppression in Nicotiana spp.
transgenic plants disrupts S-specific pollen rejection; therefore,
NaStEP is a novel pistil-modifier gene. Furthermore, HT-B levels within
the pollen tubes are reduced when NaStEP-suppressed pistils are
pollinated with either compatible or incompatible pollen. In wild-type
self-incompatible N. alata, in contrast, HT-B degradation occurs
preferentially in compatible pollinations. Taken together, these data
show that the presence of NaStEP is required for the stability of HT-B
inside pollen tubes during the rejection response, but the underlying
mechanism is currently unknown.
Filiaciones:
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Mexico City 04510, DF, Mexico
Department of Biochemistry, University of Missouri, Columbia, MO 5211, United States
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