Seed dormancy and germination

Koornneef, M.; Bentsink, Leónie; Hilhorst, Henk W. M.

doi:10.1016/s1369-5266(01)00219-9

Cited by 837 publications

(674 citation statements)

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“…The former delays seed germination, while the latter promotes seed germination. [3][4][5] Acordingly, favorable environmental conditions activate genes encoding ABA deactivating enzymes and those encoding GA biosynthetic enzymes. 6 Even under favorable conditions, seed germination can be delayed by other factors, such as high salinity.…”

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confidence: 99%

Gibberellic acid-mediated salt signaling in seed germination

Kim

Park

2008

Plant Signaling & Behavior

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salinity delays seed germination by reducing GA biosynthesis. 7 ABA is a major plant growth hormone mediating plant responses to high salinity, suggesting that the salt effects on seed germination would depends on this growth hormone. We observed that the GA synthetic enzyme gene GA3ox1 is significantly repressed by high salinity. In particular, the salt repression of GA3ox1 is independent of ABA. The GA3ox1 transcription is efficiently repressed by high salinity even in the ABA-deficient aba3-1 mutant to a level comparable to that observed in control plants treated with high salt. These observations support that an ABA-independent salt signaling pathway is also involved in the GA regulation of seed germination.NTL8 is a membrane-bound NAC transcription factor in Arabidopsis. 8 It is unique among the NTL members in that the NTL8 transcription is induced by high salinity specifically in the cold-imbibed seed. While germination of control seeds is greatly reduced in the presence of high salt, that of the ntl8-1 mutant seeds is resistant to high salinity. In contrast, seeds of the transgenic plants overexpressing an active NTL8 form (NTL8ΔC) germinated very poorly under high salt conditions, indicating that NTL8 plays a role in the salt regulation of seed germination. However, the NTL8 transcription is unaffected by ABA, and germination of the ntl8-1 knockout mutant seeds is reduced by ABA to a degree similar to that of control seeds under the same conditions. It is therefore evident that NTL8-mediated salt signaling is independent of ABA.It is notable that NTL8-mediated salt regulation of seed germination is intimately related to GA signaling. RGL2 is one of the DELLA proteins that negatively regulate GA signals. 9 When GA biosynthesis is induced, the RGL2 protein is degraded via the ubiquitin-dependent degradation pathway, causing promotion of seed germination. 10 The Arabidopsis GA biosynthetic mutant, ga1-3, does not germinate in the absence of exogenously applied GA, indicating that GA is essential for seed germination. In contrast, the ga1-3 rgl2 double mutant seeds germinate nearly 100% even in the absence of exogenous GA application, indicating that RGL2 is a negative regulator of GA function in seed germination. 9 However, recent studies strongly support that there would be additional negative regulators other than RGL2 in GA signaling. 11,12 NTL8 is dramatically induced in the imbibed seed, and its induction is further elevated by cold treatment. However, the NTL8 induction decreases to a basal level within 24 hours after cold imbibition. This pattern is very similar to that of RGL2. Germination of the ntl8-1 mutant seeds is nearly 100% in the presence of 100 μM paclobutrazol (PAC), an inhibitor of GA synthesis. The NTL8 protein is released from the membranes through proteolytic cleavage. We found that this activation process is triggered in the PAC-treated Seed germination initiates the postembryonic development of plants, which determines successful seedling establishment and plant propagation. It is th...

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confidence: 99%

Gibberellic acid-mediated salt signaling in seed germination

Kim

Park

2008

Plant Signaling & Behavior

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“…Experiments to identify this 'hatching enzyme' have been conducted in a variety of species and have provided evidence for the contribution of various cell wall-modifying proteins (e.g. endo-β-1,4-mannanases, endo-β-1,3-glucanases and expansins) (Bewley, 1997;Hilhorst et al, 1998;Koornneef et al, 2002;LeubnerMetzger, 2003). Expression of endo-β-1,4-mannanase in the micropylar endosperm of coffee is associated with the second phase of endosperm weakening and is inhibited by ABA (da Silva et al, 2004).…”

Section: Aba Endosperm Hydrolases and Endosperm Weakening In Establimentioning

confidence: 99%

“…Environmental factors and plant hormones (e.g. gibberellins (GA), abscisic acid (ABA), brassinosteroids and ethylene) are regulators of germination and/or dormancy (Koornneef et al, 2002;Kucera et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Emerging and established model systems for endosperm weakening.

Leubner‐Metzger¹,

Kucera²,

Müller³

et al. 2007

Seeds: Biology, Development and Ecology. Proceedings of the Eighth International Workshop on Seeds, Brisbane, Australia, May 20

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Endosperm rupture is the main germination-limiting process in members of the Asteraceae (e.g. lettuce (Lactuca sativa L.) ) and Solanaceae (e.g. tomato (Lycopersicon esculentum Mill.) and tobacco (Nicotiana tabacum L.). About four decades ago a 'hatching enzyme' was proposed to cause endosperm weakening (i.e. a decline in the mechanical resistance of the micropylar endosperm), which is likely to be essential for seeds to complete germination. Although, there are established model systems among Asteraceae and Solanaceae for endosperm weakening, its molecular mechanism(s) still remain(s) a mystery. No single 'hatching enzyme' or universal molecular mechanism has been demonstrated explicitly. For the time being, the provisional conclusion is that endosperm weakening is likely to be achieved by the collaborative or successive action of several distinct molecular mechanisms. The knowledge gained from these established model systems will be compared and discussed. However, consideration of their severe experimental limitations shows that there is an urgent need for novel model systems. Such an optimal system has been recently found within the Brassicaceae. In this emerging model system for endosperm weakening, a complete study of the process is possible on each experimental level, from the direct measurement of the weakening by 'puncture force' to molecular investigations (e.g. proteome and genome transcriptome analyses).

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“…Failure to germinate may be due to various external or internal factors such as seed conservation, seed viability, dormancy or seed-coat-imposed inhibition (Koornneef et al, 2002). Since seed germination can be influenced by a large number of parameters, all the analyses were performed on several independent lines to avoid misinterpretations.…”

Section: Stratification Provokes Atbp80a' Seed Germinationmentioning

confidence: 99%

Relationship between allelic state of T-DNA and DNA methylation of chromosomal integration region in transformed Arabidopsis thaliana plants

2005

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T-DNA insertions are currently used as a tool to introduce, or knock out, specific genes. The expression of the inserted gene is frequently haphazard and up to now, it was proposed that transgene expression depends on the site of insertion within the genome, as well as the number of copies of the transgene. In this paper, we show that the allelic state of a T-DNA insertion can be at the origin of epigenetic silencing. A T-DNA insertional mutant was characterized to explore the function of AtBP80a', a vacuolar sorting receptor previously associated with germination. Seeds homozygous for the T-DNA do not germinate, but this can be overcome by a cold treatment and maintained by the following generations. The nongerminating phenotype is only observed in homozygous seed produced by heterozygous plants indicating that it is correlated with the allelic state of the T-DNA in parental lines. Analysis of the region between the T-DNA insertion and the ATG codon of atbp80a' showed that cytosine methylation is highly enhanced in chromatin containing the T-DNA. Data presented here show that an unpaired DNA region during meiosis could be at the origin of a de novo cytosine methylation mechanism.

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Seed dormancy and germination

Cited by 837 publications

References 66 publications

Gibberellic acid-mediated salt signaling in seed germination

Gibberellic acid-mediated salt signaling in seed germination

Emerging and established model systems for endosperm weakening.

Relationship between allelic state of T-DNA and DNA methylation of chromosomal integration region in transformed Arabidopsis thaliana plants

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