Characterization of cDNA clones for differentially expressed genes in embryos of dormant and nondormant Avena fatua L. caryopses

Abstract

The molecular regulation of seed dormancy was investigated using differential display to visualize and isolate cDNAs representing differentially expressed genes during early imbibition of dormant and nondormant Avena fatua L. embryos. Of about 3000 cDNA bands examined, 5 cDNAs hybridized with mRNAs exhibiting dormancy-associated expression patterns during the first 48 h of inhibition, while many more nondormancy-associated cDNAs were observed. Dormancy-associated clone AFD1 hybridized with a 1.5 kb mRNA barely detectable in dry dormant and nondormant embryos that became more abundant in dormant embryos after 24 h of imbibition. Clone AFD2 hybridized with two mRNAs, a 1.3 kb message constitutively expressed in dormant and nondormant embryos and a 0.9 kb message present at higher levels in dormant embryos after 3 h of imbibition. Nondormancy-associated clones AFN1, AFN2 and AFN3 hybridized with 1.5 kb, 1.7 kb and 1.1 kb mRNAs, respectively, that were more abundant in nondormant embryos during imbibition. Expression patterns of some mRNAs in dormant embryos induced to germinate by GA3 treatment were different than water controls, but were not identical to those observed in nondormant embryos. DNA sequence analysis revealed 76% sequence identity between clone AFN3 and a Citrus sinensis glutathione peroxidase-like cDNA, while significant sequence similarities with known genes were not found for other clones. Southern hybridization analyses showed that all clones represent low (1 to 4) copy number genes.

The expression of a Vp1-like gene and seed dormancy in Mesembryanthemum crystallinum.

“…If it is the function of MVP1 to maintain L seeds dormant, it is a reasonable assumption that a CHXdependent reduction of Mvp1 gene expression would break dormancy. The results confirm observations by others that had indicated maintenance of dormancy as an active process, requiring transcription and protein synthesis (Bewley and Black 1994, Goldmark et al, 1992, Johnson et al, 1995.…”

“…The mechanisms for maintenance and termination of dormancy are not known in detail, but several approaches have recently brought progress, mainly through the study of genes that are active in dormant seeds. Expression studies have been used to trace the appearance and disappearance of transcripts in dormant seeds or embryos and to follow their fate during after-ripening (Dyer 1993, Goldmark et al, 1992, Johnson et al, 1995, Li and Foley 1995 and biochemical studies have been performed that traced fructose-2,6-bisphosphate in dormant seeds (Larondelle et al, 1987). Mutants of Arabidopsis thaliana with altered seed dormancy have been obtained (LeonKloosterziel et al, 1996).…”

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“…Many of these products have sequence homology with proteins involved in desiccation tolerance or protection against various injuries and with storage proteins [9][10][11][12][13][14]. Identifying these functions is important for understanding the differences between the dormant and non-dormant states, but to date no 'switch' function that could be involved in the choice between maintenance and release of dormancy and germinating has been discovered by these approaches.…”

Glutathione peroxidase genes in Arabidopsis are ubiquitous and regulated by abiotic stresses through diverse signaling pathways

“…Since then, several GPX cDNAs have been isolated from Citrus sinensis (Holland et al, 1993), Avena fatua (Johnson et al, 1995), Arabidopsis thaliana (Sugimoto and Sakamoto, 1997), Brassica campestris (Eshdat et al, 1997), Spinacia oleracea , Helianthus annuus (Roeckel-Drevet et al, 1998), Lycopersicon esculentum (Depe Á ge et al, 1998), Pisum sativum (Mullineaux et al, 1998), Oryza sativa (Li et al, 2000a), and Chinese cabbage (Jung et al, 2002). In addition, database searches show that many other expressed sequence tags (ESTs) with homology to GPXs exist in plants.…”