Characterization of a polyubiquitin gene from Arabidopsis thaliana

Abstract

Ubiquitin DNA sequences were isolated from the higher plant Arabidopsis thaliana L. by screening a lambda-gt11 genomic library with antibodies raised against oat and human ubiquitin. DNA sequence analysis showed that the predicted protein sequence is 100% conserved with that found in oat and barley and differs by only three residues to that found in animals. This gene (UBQ4) encodes a ubiquitin polyprotein with five repeats contiguously linked with no intervening sequences in the coding region and a C-terminal extension of Ser-Phe. Genomic Southern blot analysis showed that ubiquitin sequences comprise a multigene family of approximately 11 members in Arabidopsis. Northern blot analysis identified at least four transcript size classes, which accumulate in sizes ranging from 800 to 1900 bases. A 5'-specific probe for the UBQ4 gene was used to show that after 2 h heat shock stress, the steady state mRNA level decreased significantly in flowers/buds but not in leaves. The UBQ4 transcript accumulates in a differential manner, accumulating to higher levels in germinating tissue, etiolated tissue, and flowers/buds than in mature leaves, roots, or stems.

Differential Accumulation of Sunflower Tetraubiquitin mRNAs during Zygotic Embryogenesis and Developmental Regulation of Their Heat-Shock Response

“…As found for other plant ubiquitins (Burke et al, 1988;Binet et al, 1989;Christensen and Quail, 1989), UbiS differs from yeast and animal ubiquitins by two or three conserved amino acid changes (respectively, at positions 29 and 57 and 19, 24, and 57; data not shown). The last ubiquitin repeat in UbiS is followed by an additional Phe codon (TTT; Fig.…”

“…1). This is the same extra amino acid found before the stop codon in several plant ubiquitins (Burke et al, 1988;Fortin et al, 1988;Binet et al, 1989). DNA sequence similarity between the different ubiquitin repeats in UbiS ranged from 76.7% to 86.8%.…”

“…Both types of gene fusions belong to multigene families of moderate size, even in plants with a very small genome such as Arabidopsis (Burke et al, 1988;Callis et al, 1990). This, together with observation of differential regulation of severa1 plant ubiquitin genes, has suggested that their multiplicity and diversity reflect an evolutionary divergence of their gene regulation to cope with different specific tasks, such as functions related to cell proliferation and dedifferentiation (Gausing and Barkardottir, 1986;Jamet et al, 1990;Genschik et al, 1992); stress, light, or hormone responses (Burke et al, 1988;Binet et al, 1991;Hoffman et al, 1991;Garbarino et al, 1992;Genschik et al, 1992;Reynolds and Hooley, 1992); and organ (flower, leaf, etc.) development (Gausing and Barkardottir, 1986;Burke et al, 1988;Hoffman et al, 1991;Garbarino et al, 1992).…”

Differential Interactions of Promoter Elements in Stress Responses of the Arabidopsis Adh Gene

“…RNA was immobilized by UV cross-linking. SP6 and T7 RNA polymerase transcription was used to generate [32P]UTP-labeled probes of the ADH, GUS, NPTII, and Arabidopsis ubiquitin (Burke et al, 1988) genes using linearized plasmids as templates. RNA probe hybridizations were carried out in a Hybaid (Hybaid Ltd, Middlesex, UK) oven at 55OC using a hybridization mix containing 50% formamide, 0.25 M NaP04…”

The Effect of Heat Shock on Morphogenesis in Barley

“…The mRNA levels for ubiquitin, which is considered a low molecular mass heat stress-inducible protein (7,24), are rather low and did not show clearcut oscillations during the experiment (Fig. 4) Another interesting protein in connection with circadian rhythmicity might be barley thionin.…”