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M J Aukerman

Publications and source records attributed to M J Aukerman.

10 recordsLinked to original sources
PubMed1999

The Arabidopsis flowering-time gene LUMINIDEPENDENS is expressed primarily in regions of cell proliferation and encodes a nuclear protein that regulates LEAFY expression.

Mutations in the LUMINIDEPENDENS (LD) gene of Arabidopsis thaliana (L.) Heynh. (Arabidopsis) confer a late-flowering phenotype, indicating that LD normally functions to promote the floral transition. RNA and protein blot analyses, along with the analysis of transgenic plants containing a fusion between a genomic fragment of LD and the reporter gene uidA (GUS), indicate that LD is expressed primarily ipical proliferative regions of the shoot and root, including the shoot apical meristem and leaf primordia. Subcellular localization studies indicate that LD is a nuclear protein, consistent with its previously proposed transcriptional regulatory role. We have also found that in an apetala1 cauliflower (ap1 cal) background the ld mutation converts the reproductive shoot apex to a more vegetative state, a phenotype that is similar to that seen for the leafy (lfy) mutant. Furthermore, in situ hybridization analysis indicates that LFY levels are drastically reduced at the apex of ld ap1 cal plants after bolting. These data are consistent with the idea that at least one function of LD is to participate in the regulation of LFY.

Arabidopsis↗
PubMed1997

A deletion in the PHYD gene of the Arabidopsis Wassilewskija ecotype defines a role for phytochrome D in red/far-red light sensing.

The PHYD gene of the Wassilewskija (Ws) ecotype of Arabidopsis contains a 14-bp deletion (the phyD-1 mutation) beginning at amino acid 29 of the reading frame, resulting in translation termination at a nonsense codon 138 nucleotides downstream of the deletion end point. Immunoblot analyses showed that Ws lacks phyD but contains normal levels of phyA, phyB, and phyC. By backcrossing into the Ws and Landsberg erecta genetic backgrounds, we constructed sibling pairs of PHYD+ and phyD-1 lines and of phyB- PHYD+ and phyB- phyD- lines. Hypocotyl lengths after growth under white or red light increased sequentially in strains that were B+D+, B+D-, B-D+, and B-D-. In the Ws genetic background, an increase in petiole length, a reduction in cotyledon area and in anthocyanin accumulation in seedling stems, a diminished effect of an end-of-day pulse of far-red light on hypocotyl elongation, and a decrease in the number of rosette leaves at the onset of flowering were also seen sequentially in these lines. Thus, phyD, which is approximately 80% identical in amino acid sequence to phyB, acts in conjunction with phyB in regulating many shade avoidance responses. The existence of the apparently naturally occurring phyD-1 mutation indicates that phyD is not essential in some natural environments.

Apoproteins↗
PubMed1994

Isolation of LUMINIDEPENDENS: a gene involved in the control of flowering time in Arabidopsis.

Plants have evolved the ability to regulate flowering in response to environmental signals such as temperature and photoperiod. The physiology and genetics of floral induction have been studied extensively, but the molecular mechanisms that underlie this process are poorly understood. To study this process, we isolated a gene, LUMINIDEPENDENS (LD), that is involved in the timing of flowering in Arabidopsis. Mutations in this gene render Arabidopsis late flowering and appear to affect light perception. The late-flowering phenotype of the ld mutation was partially suppressed by vernalization. Genomic and cDNA clones of the LD gene were characterized. The predicted amino acid sequence of the LD protein contains 953 residues and includes two putative bipartite nuclear localization signals and a glutamine-rich region.

Alleles↗
PubMed1993

A 168 bp derivative of Suppressor-mutator/Enhancer is responsible for the maize o2-23 mutation.

From a directed transposon tagging of the maize Opaque-2 gene (O2), we have isolated a stable mutant o2 allele, o2-23. Cloning and molecular analysis of the allele revealed a 168 nucleotide insertion in the third exon of o2. The sequence of this small insertion indicated identity with the 5' and 3' ends of the 8.3 kb Suppressor-mutator/Enhancer (Spm/En) transposable element. This represents the smallest deletion derivative of Spm (dSpm) thus far characterized in maize. Genetic crosses of plants homozygous for o2-23 with plants homozygous for both an o2 null allele (o2-R) and an autonomous Spm produce stable opaque seed having no apparent sectors of vitreous endosperm. DNA fragments of the size expected if the dSpm were to excise were not detectable by Southern analysis, suggesting that this element is unable to transpose. Northern analysis detected an o2-23 mRNA that was much more abundant in o2-23 seeds lacking Spm than in o2-23 seeds containing Spm, consistent with the idea that Spm transacting functions can suppress the accumulation of the o2-23 transcript.

Alleles↗
PubMed1993

OHP1: a maize basic domain/leucine zipper protein that interacts with opaque2.

OPAQUE2 (O2) is a regulatory gene that predominantly affects the expression of the 22-kD class of zein storage protein genes at the level of transcription. The O2 gene encodes a polypeptide belonging to the basic domain/leucine zipper (bZIP) class of transcriptional regulatory proteins. Our prior analyses have demonstrated that the O2 protein binds 22-kD zein gene promoters as a homodimer in vitro and have also suggested that O2 may bind as a heterodimer in vivo. To identify cDNAs encoding other bZIP motifs that might interact with O2, a portion encoding the bZIP motif from an O2 cDNA was used to screen an endosperm cDNA library. Sequence analysis of one isolated recombinant phage indicated the presence of a bZIP motif similar to O2. The protein product of this partial cDNA, designated OHP1, can bind the O2 target site both as a homodimer and in a heterodimeric complex with O2. Whole genome DNA gel blot analysis of maize recombinant inbreds revealed two strongly hybridizing restriction fragments, neither of which mapped close to any locus known to affect zein expression. RNA gel blot analysis revealed an approximately 1.7-kb transcript that is expressed in all organs examined except the female flower and is also expressed in endosperms homozygous for o2 and other mutations that affect zein expression (opaque7, floury2, and Defective endosperm b-30). Based on these results and previously reported data, we propose models to accommodate OHP1 in the regulation of zein gene expression by O2.

Amino Acid Sequence↗
PubMed1992

Opaque-2 is a transcriptional activator that recognizes a specific target site in 22-kD zein genes.

opaque-2 (o2) is a regulatory locus in maize that plays an essential role in controlling the expression of genes encoding the 22-kD zein proteins. Through DNase I footprinting and DNA binding analyses, we have identified the binding site for the O2 protein (O2) in the promoter of 22-kD zein genes. The sequence in the 22-kD zein gene promoter that is recognized by O2 is similar to the target site recognized by other "basic/leucine zipper" (bZIP) proteins in that it contains an ACGT core that is necessary for DNA binding. The site is located in the -300 region relative to the translation start and lies about 20 bp downstream of the highly conserved zein gene sequence motif known as the "prolamin box." Employing gel mobility shift assays, we used O2 antibodies and nuclear extracts from an o2 null mutant to demonstrate that the O2 protein in maize endosperm nuclei recognizes the target site in the zein gene promoter. Mobility shift assays using nuclear proteins from an o2 null mutant indicated that other endosperm proteins in addition to O2 can bind the O2 target site and that O2 may be associated with one of these proteins. We also demonstrated that in yeast cells the O2 protein can activate expression of a lacZ gene containing a multimer of the O2 target sequence as part of its promoter, thus confirming its role as a transcriptional activator. A computer-assisted search indicated that the O2 target site is not present in the promoters of zein genes other than those of the 22-kD class. These data suggest a likely explanation at the molecular level for the differential effect of o2 mutations on expression of certain members of the zein gene family.

Base Sequence↗
PubMed1991

An arginine to lysine substitution in the bZIP domain of an opaque-2 mutant in maize abolishes specific DNA binding.

The opaque-2 (o2) locus in maize encodes a transcription factor involved in the regulation of zein storage proteins. We have shown previously that the O2 protein contains a leucine zipper domain that binds to promoters of 22-kD zein genes. In this paper we characterize an EMS-induced o2 allele, o2-676, that causes a 50% reduction in zein. We have found that the o2-676 mutant protein does not show specific recognition of zein promoter fragments because of the substitution of a lysine residue for an arginine residue within the bZIP domain of o2-676. This particular arginine is conserved within the bZIP domains of all mammalian, fungal, and plant DNA binding proteins of this class. The correlation between this mutation in o2 and the altered pattern of zein expression strongly suggests that O2 regulates transcription of certain members of the zein multigene family through direct interaction with the zein promoters and not through the transcriptional activation of some other regulator of zein gene expression.

Amino Acid Sequence↗
PubMed1990

Maize regulatory gene opaque-2 encodes a protein with a "leucine-zipper" motif that binds to zein DNA.

The opaque-2 locus (o2) in maize regulates the expression of many members of the zein multigene family of storage proteins. cDNA clones for a wild-type allele of the (o2) locus (O2) were isolated from a maize endosperm cDNA library and sequenced. We found a 258-nucleotide 5' leader sequence containing three short open reading frames followed by a sequence specifying a protein of 437 amino acids. The presumptive amino acid sequence of the protein (O2) specified by the O2 cDNA contains a "leucine-zipper" domain characteristic of some mammalian and fungal transcription activation factors. lacZ-O2 fusion constructs, using nearly the entire coding region of O2 or only a fragment specifying the leucine-zipper domain, were expressed in Escherichia coli. In an in vitro binding assay, the beta-galactosidase-O2 fusion proteins bound to two specific regions on the 5' side of the coding sequence in a zein genomic clone. This suggests that the O2 protein affects zein transcription through direct interaction with one or more zein promoter elements.

Amino Acid Sequence↗