Abscisic acid and temperature modify the levels of calmodulin in embryonic axes of Cicer arietinum

Exposure of stratified apple (Malus domestics Borkh. cv. Golden Delicious) seeds to 30C induces secondary dormancy. To determine if an increase in abscisic acid (ABA) content was associated with the loss in germination capacity, stratified seeds (3,- 6, or 9 weeks at 5C) were held at 30C for 0, 3, or 6 days. Stratification at 5C either had no effect or increased ABA content in embryonic axes, cotyledons, and seed coats. Exposure to 30C after stratification either did not affect or decreased ABA content of embryonic axes and seed coats; in contrast, cotyledonary ABA was increased. Seed coats, cotyledons, and embryonic axes stratified for 3, 6, or 9 weeks at 20C contained the same or higher levels of ABA in comparison with nonstratified seeds or seeds stratified at SC. Changes in ABA levels were not consistently correlated with changes in germination capacity during stratification or after exposure to 30C. These data suggest that changes in ABA are not related to changes in dormancy. Chemical names used: abscisic acid (ABA); butylated hydroxy-toluene (BHT); n-(trichloromethyl) thio-4-cyclohexene-1,2-dicarboximide(Captan).

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Isolation and characterization of a cDNA encoding an ACC oxidase from Cicer arietinum and its expression during embryogenesis and seed germination

Functional Plant Biology ◽

10.1071/pp97166 ◽

1998 ◽

Vol 25 (6) ◽

pp. 765 ◽

Cited By ~ 14

Author(s):

M.C. Gómez-Jiménez ◽

A.J. Matilla ◽

D. Garrido

Keyword(s):

Molecular Weight ◽

Cicer Arietinum ◽

Acc Oxidase ◽

Protein Product ◽

Transcriptional Level ◽

Mrna Levels ◽

Embryonic Axes ◽

Chick Pea ◽

Isolation And Characterization ◽

Genes Encoding

A full length cDNA (caaco1) encoding a putative ACC-oxidase (ACCO) was isolated and sequenced from embryonic axes of chick-pea (Cicer arietinum L.) seeds, which depend on ethylene synthesis for germination. The deduced protein for caaco1 has a molecular weight of 36 kDa, a high homology with other ACCOs and is apparently found in the cytosolic fraction of the cell. Heterologous expression of this cDNA confirmed that the protein product exhibits ACCO activity and a molecular weight close to 38 kDa. Southern blot analysis shows that there are at least two genes encoding ACCO in the chick-pea genome. The caaco1 mRNA levels in seeds remained constant during the initial stages of embryogenesis decreasing in the latest stages. During germination, caaco1 mRNA levels increase, reaching a maximum at 24 h, coinciding with the maximum percentage of germination (when all seeds are germinated), ACCO activity and ethylene production. It is interesting that there is a shift in the tissue source of the caaco1 mRNA during embryogenesis and germination. While the bulk of the expression was detected in cotyledons during embryogenesis, it was the embryonic axis that provided most of the expression detected during germination. Our data suggest that during embryogenesis ACCO is regulated at the translational level, but during germination at the transcriptional level.

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