Seed dormancy release in Arabidopsis Cvi by dry after‐ripening, low temperature, nitrate and light shows common quantitative patterns of gene expression directed by environmentally specific sensing

Abstract

SummaryThe depth of seed dormancy can be influenced by a number of different environmental signals, but whether a common mechanism underlies this apparently similar response has yet to be investigated. Full-genome microarrays were used for a global transcript analysis of Arabidopsis thaliana Cape Verde Island accession seeds exposed to dry after-ripening (AR), or low temperature, nitrate and light when imbibed. Germination studies showed that the sensitivity of imbibed seeds to low temperature, nitrate and light was dependant upon the length of time spent AR following harvest. Seeds had an absolute requirement for light to complete dormancy release in all conditions, but this effect required an exposure to a prior dormancy relieving environment. Principal component analyses of the expression patterns observed grouped physiological states in a way that related to the depth of seed dormancy, rather than the type of environmental exposure. Furthermore, opposite changes in transcript abundance of genes in sets associated with dormancy, or dormancy relief through AR, were also related to the depth of dormancy and common to different environments. Besides these common quantitative changes, environment-specific gene expression patterns during dormancy relief are also described. For example, higher transcript abundance for genes linked to the process of nitrate accumulation, and nitrate reduction was associated with dormancy relief. The quantity of GA3ox1 transcripts increased during dormancy relief in all conditions, in particular when dormancy relief was completed by exposure to light. This contrasts with transcripts linked to abscisic acid (ABA) synthesis, which declined. The results are consistent with a role for the ABA/gibberellic acid balance in integrating dormancyrelieving environmental signals.

Induction of Dormancy in Arabidopsis Summer Annuals Requires Parallel Regulation of DOG1 and Hormone Metabolism by Low Temperature and CBF Transcription Factors

“…In the dormant low-temperature-set seeds, cell wall modification, heat shock, and protein degradation were the most prominent categories, whereas in the low dormant seeds, translation, photosynthesis, seed storage proteins, and ethylene were better represented. Broadly speaking, this result is in line with previous studies that have compared seed dormancy states (Finch-Savage et al, 2007), which also identified increased gene expression associated with translation and photosynthesis as indicative of low dormant states. We confirmed the differential expression in dry seeds set at 10 or 208C by real-time PCR using independent samples ( Figure 1E).…”

“…In nature, primary dormant seeds must remain ungerminated in darkness to enter the soil seed bank, where low temperature drives the transition of imbibed seeds into secondary dormancy (Finch-Savage et al, 2007). To test this, we performed experiments testing the ability of seeds matured at three temperatures to resist germination in the dark during extended chilling ( Figure 1G).…”

Seed dormancy is a dynamic state: variable responses to pre- and post-shedding environmental signals in seeds of contrastingArabidopsisecotypes

“…Nitrate as a spatial signal Nitrate has long been known as one of the key variables in the loss of seed dormancy and promotion of germination (Baskin and Baskin, 1998;Alboresi et al, 2005;Finch-Savage et al, 2007;Matakiadis et al, 2009). Seeds use nitrate sensing as a gap detection mechanism, as nitrate levels inform about the presence of competing plants that deplete soil nitrate (Pons, 1989).…”

Acclimation of metabolism to light in Arabidopsis thaliana: the glucose 6‐phosphate/phosphate translocator GPT2 directs metabolic acclimation

“…In wild‐type plants, GPT2 expression is induced in imbibed seeds (Finch‐Savage et al . 2007), in response to exogenous and endogenous increases in sucrose (Lloyd & Zakhleniuk 2004; Gonzali et al . 2006), in response to an increase in light intensity (Athanasiou et al .…”