Lettuce Seed Germination

Cantliffe, Daniel J.; Sung, Yunsick; Nascimento, W. M. O. do

doi:10.1002/9780470650776.ch5

Cited by 12 publications

(11 citation statements)

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“…Abscisic acid (ABA), gibberellins (GA), and ethylene have been implicated in regulating germination and dormancy in lettuce seeds in relation to light and temperature, with ABA inhibiting and GA and ethylene promoting germination (Cantliffe et al 2000 ; Kucera et al 2005 ). A key regulated step in ABA biosynthesis is catalyzed by 9- cis -epoxycarotenoid dioxygenase (NCED), which cleaves 9- cis -xanthophyll to xanthoxin, a precursor of ABA (Tan et al 2003 ; Lefebvre et al 2006 ).…”

Section: Introductionmentioning

confidence: 99%

A genetic locus and gene expression patterns associated with the priming effect on lettuce seed germination at elevated temperatures

Schwember

Bradford

2010

Plant Mol Biol

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Seeds of most cultivated varieties of lettuce (Lactuca sativa L.) fail to germinate at warm temperatures (i.e., above 25–30°C). Seed priming (controlled hydration followed by drying) alleviates this thermoinhibition by increasing the maximum germination temperature. We conducted a quantitative trait locus (QTL) analysis of seed germination responses to priming using a recombinant inbred line (RIL) population derived from a cross between L. sativa cv. Salinas and L. serriola accession UC96US23. Priming significantly increased the maximum germination temperature of the RIL population, and a single major QTL was responsible for 47% of the phenotypic variation due to priming. This QTL collocated with Htg6.1, a major QTL from UC96US23 associated with high temperature germination capacity. Seeds of three near-isogenic lines (NILs) carrying an Htg6.1 introgression from UC96US23 in a Salinas genetic background exhibited synergistic increases in maximum germination temperature in response to priming. LsNCED4, a gene encoding a key enzyme (9-cis-epoxycarotinoid dioxygenase) in the abscisic acid biosynthetic pathway, maps precisely with Htg6.1. Expression of LsNCED4 after imbibition for 24 h at high temperature was greater in non-primed seeds of Salinas, of a second cultivar (Titan) and of NILs containing Htg6.1 compared to primed seeds of the same genotypes. In contrast, expression of genes encoding regulated enzymes in the gibberellin and ethylene biosynthetic pathways (LsGA3ox1 and LsACS1, respectively) was enhanced by priming and suppressed by imbibition at elevated temperatures. Developmental and temperature regulation of hormonal biosynthetic pathways is associated with seed priming effects on germination temperature sensitivity.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-009-9591-x) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 99%

A genetic locus and gene expression patterns associated with the priming effect on lettuce seed germination at elevated temperatures

Schwember

Bradford

2010

Plant Mol Biol

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“…In both cases, lettuce seeds are often exposed to higher than the optimal temperatures, which results in poor and nonuniform germination, affecting stand establishment. The optimum temperature for germination of many lettuce cultivars is between 15 and 22°C and germination may be inhibited above 27°C (Cantliffe et al, 2000).…”

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Structural Changes in Lettuce Seed During Germination at High Temperature Altered by Genotype, Seed Maturation Temperature, and Seed Priming

Sung¹,

Cantliffe²,

Nagata³

et al. 2008

J. Amer. Soc. Hort. Sci.

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To investigate thermotolerance in seeds of lettuce (Lactuca sativa L.), primed, nonprimed, or seeds matured at 20/10 and 30/20 °C (day/night on a 12-h photoperiod) were imbibed at 36 °C for various periods and then dissected. Structural changes in seed coverings in front of the radicle tip were observed during germination at high temperature. Thermotolerant genotypes, ‘Everglades’ and PI 251245, were compared with a thermosensitive cultivar, ‘Dark Green Boston’. In all seeds that germinated, regardless of seed maturation temperature or priming, a crack appeared on one side of the cap tissue (constriction of the endosperm membrane near the basal end of the seed) at the micropylar region and the endosperm separated from the integument in front of the radicle tip. Additional changes took place during imbibition in these seeds; the protein bodies in the vacuoles enlarged and gradually depleted, large empty vacuoles formed, the cytoplasm condensed, the endosperm shrank, the endosperm cell wall dissolved and ruptured, and then the radicle elongated toward this ruptured area. The findings suggested that the endosperm layer presented mechanical resistance to germination in seeds that could not germinate at 36 °C. Weakening of this layer was a prerequisite to radicle protrusion at high temperature. Seeds of ‘Dark Green Boston’, ‘Everglades’, and PI 251245 matured at 30/20 °C had greater thermotolerance than those matured at 20/10 °C. Results of the anatomical study indicated that the endosperm cell walls in front of the radicle of seeds matured at 30/20 °C were more readily disrupted and ruptured during imbibition than seeds matured at 20/10 °C, suggesting a reason why these seeds could germinate quickly at supraoptimal temperatures. Similar endosperm structural alterations also were observed in primed seeds. Priming led to rapid and uniform germination, circumventing the inhibitory effects of high temperatures. From anatomical studies conducted to identify and characterize thermotolerance in lettuce seed germination, we observed that genotype, seed maturation temperature, or seed priming had the ability to reduce physical resistance of the endosperm by weakening the cell wall and by depleting stored reserves leading to cell collapse.

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“…Lettuce seeds display little primary dormancy, but germination is strongly inhibited by warm temperatures during imbibition, a type of relative dormancy termed thermoinhibition (24,25), resulting in reduced crop establishment during warm seasons (26). Previously, we genetically mapped and functionally characterized the role of L. sativa 9-cis-EPOXYCAROTENOID DIOXYGENASE4 (LsNCED4), a gene encoding a key regulated enzyme in ABA biosynthesis, in lettuce seed thermoinhibition (24,25,27).…”

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DELAY OF GERMINATION1 ( DOG1 ) regulates both seed dormancy and flowering time through microRNA pathways

Huo

Wei

Bradford

2016

Proc. Natl. Acad. Sci. U.S.A.

166

149

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Seed germination and flowering, two critical developmental transitions in plant life cycles, are coordinately regulated by genetic and environmental factors to match plant establishment and reproduction to seasonal cues. The DELAY OF GERMINATION1 (DOG1) gene is involved in regulating seed dormancy in response to temperature and has also been associated genetically with pleiotropic flowering phenotypes across diverse Arabidopsis thaliana accessions and locations. Here we show that DOG1 can regulate seed dormancy and flowering times in lettuce (Lactuca sativa, Ls) and Arabidopsis through an influence on levels of microRNAs (miRNAs) miR156 and miR172. In lettuce, suppression of LsDOG1 expression enabled seed germination at high temperature and promoted early flowering in association with reduced miR156 and increased miR172 levels. In Arabidopsis, higher miR156 levels resulting from overexpression of the MIR156 gene enhanced seed dormancy and delayed flowering. These phenotypic effects, as well as conversion of MIR156 transcripts to miR156, were compromised in DOG1 loss-of-function mutant plants, especially in seeds. Overexpression of MIR172 reduced seed dormancy and promoted early flowering in Arabidopsis, and the effect on flowering required functional DOG1. Transcript levels of several genes associated with miRNA processing were consistently lower in dry seeds of Arabidopsis and lettuce when DOG1 was mutated or its expression was reduced; in contrast, transcript levels of these genes were elevated in a DOG1 gain-of-function mutant. Our results reveal a previously unknown linkage between two critical developmental phase transitions in the plant life cycle through a DOG1-miR156-miR172 interaction.T he life cycles of flowering plants are characterized by distinct phase transitions such as from seed to seedling (germination) or from vegetative to reproductive development (flowering) (1). The timing of germination and flowering both require precise environmental sensing and integrated responses to multiple inputs so that developmental transitions can be accurately matched to seasonal conditions (1-3). Seeds use temperature as a signal of the seasonal and current environmental conditions to determine opportune times to germinate with respect to the potential for seedling survival (2, 4, 5). Similarly, in many plants the transition from vegetative to floral development occurs in response to environmental cues, particularly temperature and day length (6, 7). Ecological and evolutionary studies have found that seed germination and flowering traits within species are coadapted across habitat ranges (8-11). Seed dormancy and germination are regulated primarily by the antagonistic actions of the plant hormones gibberellin (GA; promotive) and abscisic acid (ABA; inhibitory), whose synthesis and action vary in response to environmental signals (12). Recent studies indicate that canonical genes regulating flowering, such as FLOWERING LOCUS T (FT) and FLOWERING LOCUS C (FLC), are also involved in the transition from seed dormanc...

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Lettuce Seed Germination

Cited by 12 publications

References 178 publications

A genetic locus and gene expression patterns associated with the priming effect on lettuce seed germination at elevated temperatures

A genetic locus and gene expression patterns associated with the priming effect on lettuce seed germination at elevated temperatures

Structural Changes in Lettuce Seed During Germination at High Temperature Altered by Genotype, Seed Maturation Temperature, and Seed Priming

DELAY OF GERMINATION1 ( DOG1 ) regulates both seed dormancy and flowering time through microRNA pathways

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