Role of Gibberellins in Phytochrome-Mediated Lettuce Seed Germination

Inoue, Yasunori

doi:10.1007/978-1-4612-3002-1_28

Cited by 9 publications

(6 citation statements)

References 12 publications

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“…A peak of epi-DPA was not detected in seeds or medium (data not shown). The levels of ABA, PA, and DPA in each culture medium were also measured and were shown to be unaffected by light treatment, suggesting that these compounds in medium had diffused from the seed coats (Inoue, 1990). These results indicated that ABA reduction by R treatment in the seeds was due to metabolism and not to exudation, and catabolic intermediates, such as PA, were quickly catabolized in lettuce seeds.…”

Section: Measurement Of Aba and Its Catabolites In Germinating Lettucmentioning

confidence: 89%

Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Sawada

Aoki²,

Nakaminami³

et al. 2008

Plant Physiol.

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Germination of lettuce (Lactuca sativa) 'Grand Rapids' seeds is regulated by phytochrome. The action of phytochrome includes alterations in the levels of gibberellin (GA) and abscisic acid (ABA). To determine the molecular mechanism of phytochrome regulation of ABA metabolism, we isolated four lettuce cDNAs encoding 9-cis-epoxycarotenoid dioxygenase (biosynthesis; LsNCED1-LsNCED4) and four cDNAs for ABA 8#-hydroxylase (catabolism; LsABA8ox1-LsABA8ox4). Measurements of ABA and its catabolites showed that a decrease in ABA level coincided with a slight increase in the level of the ABA catabolite phaseic acid after red light treatment. Quantitative reverse transcription-polymerase chain reaction analysis indicated that ABA levels are controlled by phytochrome through down-regulation of LsNCED2 and LsNCED4 expression and up-regulation of LsABA8ox4 expression in lettuce seeds. Furthermore, the expression levels of LsNCED4 decreased after GA 1 treatment, whereas the levels of expression of the other two genes were unaffected. The LsNCED4 expression was also down-regulated by red light in lettuce seeds in which GA biosynthesis was suppressed by AMO-1618, a specific GA biosynthesis inhibitor. These results indicate that phytochrome regulation of ABA metabolism is mediated by both GA-dependent and -independent mechanisms. Spatial analysis showed that after red light treatment, the ABA decrease on the hypocotyl side was greater than that on the cotyledon side of lettuce seeds. Moreover, phytochrome-regulated expression of ABA and GA biosynthesis genes was observed on the hypocotyl side, rather than the cotyledon side, suggesting that this regulation occurs near the photoperceptive site.Plants undergo correct morphogenesis by responding to light and adapt to various forms of light. In addition to imbibition, some seeds require light to germinate and are called photoblastic seeds. Photoblastic seeds germinate after irradiation with red light (R; wavelength approximately 600-700 nm), and this effect of R is cancelled by successive irradiation with far-red light (FR; wavelength approximately 700-750 nm). The effects of R and FR are reversible. This type of germination, called photogermination, was discovered by experiments using lettuce (Lactuca sativa) 'Grand Rapids' seeds (Borthwick et al., 1952). The energy from wavelengths of R is mainly required for photosynthesis. This strategy allows survival of small seeds in which storage substances are low, such as the seeds of lettuce, tomato (Solanum lycopersicum), tobacco (Nicotiana tabacum), and Arabidopsis (Arabidopsis thaliana). The typical reversible photoreaction of lettuce seeds allowed Butler et al. (1959) to detect the pigment that acts as the R/FR receptor in extracts from etiolated cotyledons of Brassica rapa and etiolated shoots of Zea mays using differential spectrophotometry, and this photoreceptor was named phytochrome.Many studies to elucidate the mechanisms of photoblastic lettuce seed germination have been carried out for over a half century, including biochemica...

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Section: Measurement Of Aba and Its Catabolites In Germinating Lettucmentioning

confidence: 89%

Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Sawada

Aoki²,

Nakaminami³

et al. 2008

Plant Physiol.

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“…Red light induces seed germination and far-red light, given after red light, completely suppresses the effect of red light (Borthwick et al 1952). Inoue (1990) reported that decoated Grand Rapids seeds germinated in the dark without * Present Address: The Institute of Physical and Chemical Research, Wako-shi, Saitama 351-01, Japan Plant Materials. Mature lettuce seeds (Lactuca sativa L. cv.…”

Section: Qualitative Analysismentioning

confidence: 99%

“…The Grand Rapids seeds were punctured with a sharp tungsten needle (Inoue 1990). The 20 punctured seeds were sowed in a polystyrene well (30 mm i.d.)…”

Section: Lettuce Seed Germination Assaymentioning

confidence: 99%

“…To test this hypothesis, the effects of GA1 and its possible precursor, GA20, were investigated on the germination of punctured lettuce seeds (Inoue 1990) in the dark. As shown in Fig.…”

Section: Effects Of Gas and Ga2o On The Lettuce Seed Germinationmentioning

confidence: 99%

“…red light irradiation, and suggested that the fruit wall has inhibitory effects on the seed germination. From the fruit wall, abscisic acid (ABA) was identiffed as an inhibitor of germination, its content being about 0.33 Ixg/g (Inoue 1990). On the other hand, gibberellin A3 (GA3) is known to mimic the effect of red light on the germination of lettuce seeds (De Greef and Fredericq 1983).…”

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confidence: 99%

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Light effects on endogenous levels of gibberellins in photoblastic lettuce seeds

Toyomasu

Tsuji

Yamane

et al. 1993

J Plant Growth Regul

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Gibberellin A 1 (GA1), 3-epi-GAl, GA17, GA19, GA2o, and GA77 were identified by Kovats retention indices and full-scan mass spectra from gas chromatography-mass spectrometry analysis of a purified extract of mature seeds of photoblastic lettuce (Lactuca sativa L. cv. Grand Rapids). Non-13-hydroxylated GAs such as GA 4 and GA 9 were not detected even by highly sensitive radioimmunoassay. These results show that the major biosyn-

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