75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

353 Natural Variation Studies For Circadian Clock Input Components In Arabidopsis thaliana
Eleni Boikoglou 1, 2 , Amanda Davis 1 , Ferenc Nagy 2 , Seth Davis 1
1
Max Planck Institute for Plant Breeding Research, Koeln, 50829, Germany, 2 Institute of Plant Biology,
Biological Research Center, H-6701, Szeged, Hungary
The circadian clock is an internal mechanism that regulates various processes in the plant life cycle. The clock
is entrained by environmental cues, such as light and temperature. Although light input has extensively been studied,
temperature’s role as a clock input signal is as yet unraveled. Recently, studies on circadian mutants have shown that
temperature cycles are capable to entrain the clock. Our interest is to dissect the genes that function in this thermo-sensory
pathway. Presumably, the genetic architecture of thermo-perception will be similar to, but different from, photo-perception.
In this study, natural variation is exploited with respect of thermal entrainment of the circadian clock. Arabidopsis thaliana
accessions and Recombinant Inbred Lines (RILS) were transformed using CCR2::LUC reporter. The CCR2 promoter
was chosen as its expression is under clock control, and moreover, is thermally regulated. Clock characteristic-traits
such as period, phase, and amplitude will be assessed by measuring bioluminescent rhythms of CCR2 transcriptional
outputs. Our aim is to identify, map, and characterize temperature-specific genetic components responsible for regulation
of the circadian clock. Preliminary results of various lines have revealed that there is low variation within the RILS and
high variation amongst them. Thus, it is feasible the scoring of the clock traits will contribute to QTL identification.
The identification of these genetic components will lead towards an exciting entry in the temperature entrainment of the
circadian clock.
354 Prevalence and mechanisms of F1 incompatibility in Arabidopsis thaliana
Kirsten Bomblies, Janne Lempe, Christa Lanz, Norman Warthmann, Detlef Weigel
Max Planck Institute for Developmental Biology
Postzygotic reproductive incompatibility, that is, the sterility or inviability of hybrids, dramatically illustrates
breakdown of gene coordination within a genome and is likely important in speciation. We show here that post-zygotic
incompatibilty exists among wild strains of Arabidopsis thaliana. Among over 300 hybrid combinations we identified
five F1 hybrids that show environmentally sensitive morphological defects, ranging in severity from leaf chlorosis and
twisting, to dwarfism, loss of apical dominance, severe leaf defects and growth arrest. The genetic interactions conform
to predictions of the Dobzhansky-Muller model for post-zygotic incompatibility involving two dominant loci. All five
hybrids are specific; crosses with other ecotypes did not produce abnormalities. Furthermore, hybrid combinations
among the parents of these hybrids show that different genes or alleles underlie the F1 phenotypes. Using micro-arrays,
histological and other molecular approaches, we found that these hybrids mount autoimmune responses in the absence of
pathogen challenge. Consistent with this, one of two causal regions fine-mapped in one hybrid contains two polymorphic
TIR-NBS-LRR class resistance (R) genes. We are now testing candidate genes using artificial micro-RNAs and are
mapping the causal loci for the remaining four hybrids. Intriguingly, our Arabidopsis hybrid incompatibility phenotypes
(including temperature sensitivity) are remarkably similar to a common F1 hybrid syndrome, hybrid necrosis or weakness,
which occurs in a wide variety of other plant species. Based on our data, we hypothesize that rapidly-evolving R genes
evolve aberrant interactions with gene variants present in conspecific individuals, resulting in hybrid incompatibility
at detectable frequency in Arabidopsis and other plant species. This parallels findings in animals that implicate rapidly
evolving genes in reproductive isolation and has important implications for plant evolution and speciation.