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.
Temporal and spatial changes in the patterns of PCD are responsible for male sterility of female flowers in O. stenopetala. Male fertility requires the co-ordination of different events, which, when altered, can lead to male sterility and to functionally unisexual individuals. PCD could be a widespread mechanism in the determination of functionally dioecious species.
La crioconservación de semillas representa una alternativa para la conservación a largo plazo de germoplasma forestal, sobre todo de especies tropicales intermedias o recalcitrantes, cuya viabilidad decae rápidamente bajo condiciones estándares de almacenamiento. Por ello, se evaluó en semillas de cedro rojo el impacto del congelamiento rápido en nitrógeno líquido (N2L) sobre la germinación sensu stricto y desarrollo temprano de la plántula. Para este fin, semillas deshidratadas o sin deshidratar se sometieron a pretratamientos de encapsulación/deshidratación en presencia de agentes osmoprotectores (LS, PVS2 y PVS3), previo a su congelación en N2L. Después de la descongelación a temperatura ambiente, se compararon la capacidad y velocidad de germinación de las semillas de los distintos tratamientos, así como el establecimiento, supervivencia y crecimiento de las plántulas después de cuatro meses en vivero. Los resultados muestran que las semillas de cedro rojo tienen la capacidad de sobrevivir el congelamiento rápido, aunque esto tuvo en general un efecto perjudicial durante las etapas de germinación y emergencia temprana, el cual fue menos severo en semillas sin encapsular. No obstante, los pretratamientos favorecieron la supervivencia de la plántula en vivero; el sistema radicular tuvo mayores afectaciones que la parte aérea en todos los tratamientos de congelación, lo cual incidió en una alta relación PSA/PSR. Se concluye que las semillas de Cedrela odorata sometidas al congelamiento rápido tienen el potencial de sobrevivir, germinar y producir plántulas para trasplante en vivero, aunque es necesario afinar el protocolo para optimizar la respuesta.
Seed banks represent an important strategy for the conservation of forest genetic resources, although a basic understanding of the physiological changes that seeds undergo during storage that affect quality and germination is still lacking for most tropical and subtropical species. Here, we describe the optimisation of an RNA isolation procedure and reference gene normalisation for expression analysis in Cedrela odorata (cedro or Spanish cedar) seeds during different physiological states, as well as in the steady-state stem and leaf. The expression profiles of five endogenous candidate reference genes (18S, EF1α, GAPDH, CDC27B, PP2A2) and an exogenous (HMBS) gene were evaluated by using dedicated algorithms, including Genorm, Normfinder, Bestkeeper and ΔCt. We found that the expression of all endogenous genes varied considerably in response to both ageing and hydration. Therefore, using the external HMBS was a suitable alternative to evaluate gene expression in these highly contrasting physiological conditions. The reference genes EF1α and GAPDH were the most stable, and could be used for normalisation of qRT-PCR results under specific circumstances.
The unambiguous identification of varieties within the Pseudostrobus complex is a key step to facilitate tree selection and monitoring in the wild as well as in plantations. Molecular tools provide a powerful approach for species delimitation; however, the use of DNA barcodes in this group has met limited success due to widespread haplotype sharing from lineage sorting, hybridization and introgression. Here, we evaluate the utility of real-time PCR coupled with high-resolution melting (HRM) to discriminate among Pinus pseudostrobus Lindl. var. pseudostrobus, apulcensis and oaxacana, from wild populations in central and southern Mexico, using chloroplast DNA sequence variants located within the clpP, ycf2, trnL(UAA)–trnT(UGU) and trnI(CAU)–trnF(GAA) loci. The markers ycf2/trnL(UAA)–trnT(UGU) produced clear melting patterns that separated the varieties pseudostrobus and oaxacana from type var. apulcensis, whereas clpP discriminated over 60% of var. oaxacana individuals. This assay underlines the usefulness of these less-used DNA regions as potential biological markers and exhibits the effect of geography on allele distribution and the likely presence of hybrids among the species and varieties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.