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Abstract:
Plants modulate their growth and development based on environmental cues. The shoot apical meristem (SAM) generates leaves in a particular spatial arrangement (phyllotaxis) at defined time intervals (plastochron length). Environmental cues such as light, temperature and presence of pathogens may affect both traits although underlying mechanisms are currently unknown. Here we report co-localisation of a QTL for plastochron length with a natural variant in a pathogen response gene, suggesting a built-in trade-off between immunity and growth rates.
We screened 24 accessions of Arabidopsis thaliana in three different growth conditions to reveal extensive variation in plastochron length. Exploiting this natural variation, we performed QTL analysis in two different temperature conditions using a newly developed Recombinant Inbred Lines (RIL) population derived from Col-0 (Columbia) and Est-1 (Estland). The QTL analysis revealed a major temperature-sensitive QTL for plastochron lenght in Chromosome 4, and a co-localising major QTL for leaf lesioning, a trait peculiar to Est-1 plants. Using an Heterogenous Inbred Family (HIF48) we fine mapped the lesioning phenotype to a 12 kb region. Expression analysis suggests that the lesioning is associated with constitutive activation of pathogen response pathways; we are in the process of testing whether this response is functional. Sequence analysis of the genes present in the QTL interval reveals substantial natural variation not only between Est-1 and Col-0, but also among other wild strains. Transgenic analysis through complementation and amiRNA-mediated silencing is currently underway to confirm the causality for the QTL. The apparent co-localisation of a plastochron QTL and potential variation in pathogen response has important implications for adaptation to the environment.
