Cloning and expression of an embryo-specific mRNA up-regulated in hydrated dormant seeds

Abstract

Dormant seeds do not germinate when imbibed in water even when conditions are favorable for germination. These hydrated seeds remain viable, but growth-arrested for weeks due to unknown restrictions within the embryo. As a model system for the study of the molecular processes occurring in dormant seeds, we have chosen to examine gene expression in Bromus secalinas, a grass species that produces seeds with high levels of embryonic dormancy. Using differential screening for mRNAs present in hydrated dormant embryos, we have identified a cDNA clone, pBS128, that encodes a mRNA transcript found in the embryos of hydrated seeds of B. secalinus as well as in embryos from mature dry seeds. Striking differences in pBS128 transcript levels appear upon hydration of dormant and nondormant seeds. Upon imbibition pBS128 transcript levels increase over four-fold in dormant seeds, but rapidly decline and disappear in nondormant seeds, which subsequently germinate. The pBS128 transcript appears to be embryo-specific since the transcript is not detectable in either non-stressed or dehydrated seedling tissue. Application of 50 microM ABA to nondormant seeds arrests germination and enhances pBS128 transcript levels. The nucleotide sequence of the nearly full-length pBS128 cDNA shows no homology to other reported genes, and the putative protein sequence does not exhibit the hydrophilic characteristics of the ABA-responsive LEA (late embryogenesis abundant) proteins.

Transcripts encoding an oleosin and a dormancy‐related protein are present in both the aleurone layer and the embryo of developing barley (Hordeum vulgare L.) seeds

“…The largest ORF of the full-length B15C sequence ( Figure 2b) encodes a protein of 218 amino acids, which is identical to the protein encoded by the pBS128 cDNA from the grass species Bromus secalinus except for five amino acid substitutions (Goldmark et a/., 1992) (Figure 3b). In B. secalinus, this transcript is upregulated in dormant embryos after imbibition (Goldmark etal., 1992).…”

“…The pBS128 transcript from B. secalinus, which is maintained at a high level in dormant, but not in nondormant hydrated seeds, has been suggested to play a role in the maintenance of embryo dormancy (Goldmark et a/., 1992). The presence of this transcript in embryos of downy brome (B. tectorum), common rye (Secale cereale), wild oat (Avena fatua), jointed goatgrass (Aegilops cylirtdrica) (Goldmark et a/., 1992) and perennial ryegrass ( Figure 6, lane 10) also suggests an important function in monocot seeds.…”

Characteristics of soybean 1-Cys peroxiredoxin and its behavior in seedlings under flooding stress

“…In contrast to GmPer1a, expression of the GmPer1b gene was barely detectable in soybean plants or seeds, suggesting again that GmPer1b is a pseudogene. It has been reported that 1-Cys Prx genes of various plants, including Per1 of barley (Aalen et al 1994), pBS128 of brome grass (Goldmark et al 1992), FePer1 of buckwheat (Lewis et al 2000), R1C-Prx of rice (Lee et al 2000) and AtPer1 of Arabidopsis (Haslekås et al (A) SDS-PAGE of synthesized and purified recombinant GmPer1a. His-tagged GmPer1a was synthesized by a wheat germ expression system and then applied to a Ni-Sepharose column.…”

Seed 1-Cysteine Peroxiredoxin Antioxidants Are Not Involved in Dormancy, But Contribute to Inhibition of Germination during Stress

“…The plant 1-Cys Prx genes pBS128 from brome grass (Goldmark et al, 1992), Per1 in barley (also called B15C; Aalen et al, 1994), AtPER1 in Arabidopsis (Haslekås et al, 1998), and FePer1 from buckwheat (Fagopyrum esculentum; Lewis et al, 2000) are expressed in developing seeds. They have high expression levels during the stages of massive water loss at the end of seed development and also in the mature dry seed.…”