Gene expression profiles of Arabidopsis Cvi seeds during dormancy cycling indicate a common underlying dormancy control mechanism

Abstract

SummaryPhysiologically dormant seeds, like those of Arabidopsis, will cycle through dormant states as seasons change until the environment is favourable for seedling establishment. This phenomenon is widespread in the plant kingdom, but has not been studied at the molecular level. Full-genome microarrays were used for a global transcript analysis of Arabidopsis thaliana (accession Cvi) seeds in a range of dormant and dry after-ripened states during cycling. Principal component analysis of the expression patterns observed showed that they differed in newly imbibed primary dormant seeds, as commonly used in experimental studies, compared with those in the maintained primary and secondary dormant states that exist during cycling. Dormant and afterripened seeds appear to have equally active although distinct gene expression programmes, dormant seeds having greatly reduced gene expression associated with protein synthesis, potentially controlling the completion of germination. A core set of 442 genes were identified that had higher expression in all dormant states compared with after-ripened states. Abscisic acid (ABA) responsive elements were significantly overrepresented in this set of genes the expression of which was enhanced when multiple copies of the elements were present. ABA regulation of dormancy was further supported by expression patterns of key genes in ABA synthesis/catabolism, and dormancy loss in the presence of fluridone. The data support an ABA-gibberelic acid hormone balance mechanism controlling cycling through dormant states that depends on synthetic and catabolic pathways of both hormones. Many of the most highly expressed genes in dormant states were stress-related even in the absence of abiotic stress, indicating that ABA, stress and dormancy responses overlap significantly at the transcriptome level.

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

“…Cvi seeds tend to germinate more readily at lower temperatures, consistent with a winter-annual phenotype, while Bur seeds show the reverse response and germinate more readily at higher temperatures consistent with a summer-annual phenotype. In addition, short periods of low temperature (58C) appeared to be an efficient way to release dormancy of Bur but not Cvi, which first requires a period of AR to become sensitive to low temperature (Cadman et al, 2006;Finch-Savage et al, 2007). Germination of Ler seeds produced at 208C had high germination at low temperatures coupled to high-temperature thermodormancy.…”

“…For example, the ratio of red/far red wavelengths alters as light passes through a leaf canopy, informing about the presence of competing plants (as reviewed in Pons, 2000). In Arabidopsis, dormancy release and the completion of germination of both summer-and winter-annual ecotypes can have an absolute light dependency (Cadman et al, 2006;Finch-Savage et al, 2007;Footitt et al, 2013).…”

“…Seed yield and 1000-seed weight were measured before sealing in aluminium-foil bags and storage at 2 808C for germination experiments. A proportion of the freshly harvested Bur and Cvi seeds were placed in separate sealed bags to afterripen (AR) at 208C and 55% ERh for 8 months, matching the requirement for completion of AR in previous studies of Cvi (Cadman et al, 2006;Finch-Savage et al, 2007). In further experiments, seeds were placed in Eppendorf tubes (1.5 ml) within 50-ml screw-cap tubes sealed with Nescofilm at 208C for periods up to 210 d before germination was recorded at a range of conditions, as described below.…”

High Temperature-Induced Abscisic Acid Biosynthesis and Its Role in the Inhibition of Gibberellin Action in Arabidopsis Seeds

“…S2). Recently, by using a strongly dormant Arabidopsis accession, Cape Verde Islands (Cvi), Cadman et al (2006) reported that expression of NCED6 is up-regulated in primary dormant and secondary dormant seeds imbibed in the dark. Seo et al (2006) reported that NCED6 expression in seeds is induced during dark imbibition after farred light treatment and suppressed by subsequent red-light treatment.…”

Participation of GA3, ethylene, NO and HCN in germination of Amaranthus retroflexus L. seeds with various dormancy levels

“…Instead of burial, stratification and hormones also dry storage (after-ripening) of seeds can release dormancy in several plant species e.g., Amaranthus retroflexus (Schön-beck and Egley 1980), Arabidopsis thaliana (Cadman et al 2006), Hordeum vulgare (Gubler et al 2008), Sisymbrium officinale (Iglesias-Fernandez and Matilla 2009) and Avena fatua ). Moreover, nitrogen-containing compounds such as nitrate, nitrite, hydroxylamine and azide have been known to break dormancy of seeds (Hendricks and Taylorson 1974).…”