July 4, 2013

Source: International Society for Seed Science

Following our recent analysis of dormancy cycling in the soil seed bank using the highly dormant winter annual ecotype Cape Verdi Isle (Cvi) we recently completed a comparable analysis of the summer annual ecotype Burren (Bur). By comparing seedling emergence in the field, depth of dormancy and thermal germination response following recovery form the soil seed bank we demonstrate responses to the soil environment consistent with winter (Cvi) and summer (Bur) annual behaviour.

We show how mechanisms identified in the laboratory are coordinated in response to the soil environment to determine the dormancy cycles that result in winter and summer annual phenotypes. Our results are consistent with a seed-specific response to seasonal temperature patterns (temporal sensing) involving the gene DELAY OF GERMINATION 1 (DOG1)
that indicates the correct season, and concurrent temporally driven co-opted mechanisms that sense spatial signals, i.e. nitrate, via CBL-INTERACTING PROTEIN KINASE 23 (CIPK23) phosphorylation of the NITRATE TRANSPORTER 1 (NRT1.1), and light, via PHYTOCHROME A (PHYA). In both ecotypes studied, when all three genes have low expression there is enhanced GIBBERELLIN 3 BETA-HYDROXYLASE 1 (GA3ox1) expression, exhumed seeds have the potential to germinate in the laboratory, and the initiation of seedling emergence occurs following soil disturbance (exposure to light) in the field. Unlike DOG1, the expression of MOTHER of FLOWERING TIME (MFT) has an opposite thermal response in seeds of the two ecotypes, indicating a role in determining their different dormancy cycling phenotypes.
This work is part of a growing trend to use accessions adapted to diverse climates to explore GENE X ENVIRONMENT interactions and their role in the bet hedging strategy of dormancy cycling.

Steven Footitt, Ziyue Huang, Heather A. Clay, Andrew Mead and William E. Finch-Savage (2013) Temperature, light and nitrate sensing coordinate Arabidopsis seed dormancy cycling, resulting in winter and summer annual phenotypes. The Plant Journal 74, 1003–1015 doi: 10.1111/tpj.12186

This publication is open access and available on the following link; http://onlinelibrary.wiley.com/doi/10.1111/tpj.12186/abstract

Website: http://www.seedscisoc.org/

Published: July 5, 2013