Biomedical subjects

Stephen P Moose

Publications and source records attributed to Stephen P Moose.

8 recordsLinked to original sources

PubMed2005

microRNA172 down-regulates glossy15 to promote vegetative phase change in maize.

Shoot development in many higher plant species is characterized by phase change, where meristems and organs transition from one set of identities to another. The transition from a juvenile to adult leaf identity in maize is regulated by the APETALA2-like gene glossy15 (gl15). We demonstrate here that increasing gl15 activity in transgenic maize not only increases the number of leaves expressing juvenile traits, but also delays the onset of reproductive development, indicating that gl15 plays a primary role in the maintenance of the juvenile phase. We also show that the accumulation of a maize microRNA homologous to miR172 increases during shoot development and mediates gl15 mRNA degradation. These data indicate that vegetative phase change in maize is regulated by the opposing actions of gl15 and miR172, with gl15 maintaining the juvenile phase and miR172 promoting the transition to the adult phase by down-regulation of gl15. Our results also suggest that the balance of activities between APETALA2-like genes and miR172 may be a general mechanism for regulating vegetative phase change in higher plants.

Base Sequence↗

PubMed2004

Amino acid metabolism in maize earshoots. Implications for assimilate preconditioning and nitrogen signaling.

Nitrogen (N) is an essential requirement for kernel growth in maize (Zea mays); however, little is known about how N assimilates are metabolized in young earshoots during seed development. The objective of this study was to assess amino acid metabolism in cob and spikelet tissues during the critical 2 weeks following silking. Two maize hybrids were grown in the field for 2 years at two levels of supplemental N fertilizer (0 and 168 kg N/ha). The effects of the reproductive sink on cob N metabolism were examined by comparing pollinated to unpollinated earshoots. Earshoots were sampled at 2, 8, 14, and 18 d after silking; dissected into cob, spikelet, and/or pedicel and kernel fractions; then analyzed for amino acid profiles and key enzyme activities associated with amino acid metabolism. Major amino acids in the cob were glutamine (Gln), aspartic acid (Asp), asparagine (Asn), glutamate, and alanine. Gln concentrations dropped dramatically from 2 to 14 d after silking in both pollinated and unpollinated cobs, whereas all other measured amino acids accumulated over time in unpollinated spikelets and cobs, especially Asn. N supply had a variable effect on individual amino acid levels in young cobs and spikelets, with Asn being the most notably enhanced. We found that the cob performs significant enzymatic interconversions among Gln, alanine, Asp, and Asn during early reproductive development, which may precondition the N assimilate supply for sustained kernel growth. The measured amino acid profiles and enzymatic activities suggest that the Asn to Gln ratio in cobs may be part of a signal transduction pathway involving aspartate aminotransferase, Gln synthetase, and Asn synthetase to indicate plant N status for kernel development.

Amino Acids↗

PubMed2004

Maize selection passes the century mark: a unique resource for 21st century genomics.

The Illinois Long-Term Selection Experiment for grain protein and oil concentration in maize (Zea mays) is the longest continuous genetics experiment in higher plants. A total of 103 cycles of selection have produced nine related populations that exhibit phenotypic extremes for grain composition and a host of correlated traits. The use of functional genomics tools in this unique genetic resource provides exciting opportunities not only to discover the genes that contribute to phenotypic differences but also to investigate issues such as the response of plant genomes to artificial selection, the genetic architecture of quantitative traits and the source of continued genetic variation within domesticated crop genomes.

Genome, Plant↗

PubMed2004

The maize O2 and PBF proteins act additively to promote transcription from storage protein gene promoters in rice endosperm cells.

A transient expression assay system was employed to investigate the possible use of the maize Opaque 2 (O2) and prolamin box binding factor (PBF) proteins as transcriptional activators of rice and wheat storage protein gene promoters. When assayed in developing rice endosperm cells, either O2 or PBF alone could increase transcription from the promoter of the rice glutelin gene, Gt1. However, mutant forms of O2 and PBF that are defective in DNA binding could not. Co-transfection with both transcriptional activators resulted in an additive increase in transactivation of the Gt1 promoter. Co-bombardment of a Gt1::GUS construct with plasmids expressing the DNA binding domains of O2 and PBF in antisense orientation resulted in a decrease of GUS expression below background levels. Similar stimulatory and additive effects of O2 and PBF could be observed on the promoters from other storage protein genes including rice globulin (Glb), prolamins (RP6 and PG5a) and a wheat glutenin (Bx7). However, responsiveness of the promoters from non-storage protein genes like rice actin and CaMV 35S to O2 and PBF was insignificant. Our results indicate that the maize O2 and PBF proteins can act singly or additively as effective stimulators of heterologous storage protein promoters in developing rice endosperm cells. These data support the use of well-characterized transcription factors from maize as an effective means of increasing the expression level of recombinant proteins in developing rice seeds.

Antisense Elements (Genetics)↗

PubMed2004

The maize macrohairless1 locus specifically promotes leaf blade macrohair initiation and responds to factors regulating leaf identity.

The leaf surfaces of almost all plant species possess specialized epidermal cell types that form hairs or trichomes. Maize leaves produce three distinct types of hairs, the most prominent being the macrohairs that serve as a marker for adult leaf identity and may contribute to insect resistance. This report describes the maize macrohairless1 (mhl1) locus, which promotes macrohair initiation specifically in the leaf blade. Each of seven recessive mhl1 mutant alleles significantly reduces or eliminates macrohairs in the leaf blade. The mhl1 mutations block macrohair initiation rather than interfering with macrohair morphogenesis. Genetic mapping placed mhl1 within bin 4 on chromosome 9. A second independently segregating locus was found to partially suppress the mhl1 mutant phenotype in certain genetic backgrounds. Macrohair density was observed to increase during early adult vegetative development and then progressively decline, suggesting macrohair initiation frequency is affected by factors that act throughout shoot development. Genetic analyses demonstrated that mhl1 acts in the same pathway but downstream of factors that either promote or repress adult leaf identity. Thus, mhl1 plays a key role in integrating developmental programs that regulate leaf identity during shoot development with those that specify macrohair initiation within the leaf blade.

Alleles↗

PubMed2003

Cold tolerance of C4 photosynthesis in Miscanthus x giganteus: adaptation in amounts and sequence of C4 photosynthetic enzymes.

Field-grown Miscanthus x giganteus maintains high photosynthetic quantum yields and biomass productivity in cool temperate climates. It is related to maize (Zea mays) and uses the same NADP-malic enzyme C(4) pathway. This study tests the hypothesis that M. x giganteus, in contrast to maize, forms photosynthetically competent leaves at low temperatures with altered amounts of pyruvate orthophosphate dikinase (PPDK) and Rubisco or altered properties of PPDK. Both species were grown at 25 degrees C/20 degrees C or 14 degrees C/11 degrees C (day/night), and leaf photosynthesis was measured from 5 degrees C to 38 degrees C. Protein and steady-state transcript levels for Rubisco, PPDK, and phosphoenolpyruvate carboxylase were assessed and the sequence of C(4)-PPDK from M. x giganteus was compared with other C(4) species. Low temperature growth had no effect on photosynthesis in M. x giganteus, but decreased rates by 80% at all measurement temperatures in maize. Amounts and expression of phosphoenolpyruvate carboxylase were affected little by growth temperature in either species. However, PPDK and Rubisco large subunit decreased >50% and >30%, respectively, in cold-grown maize, whereas these levels remained unaffected by temperature in M. x giganteus. Differences in protein content in maize were not explained by differences in steady-state transcript levels. Several different M. x giganteus C(4)-PPDK cDNA sequences were found, but putative translated protein sequences did not show conservation of amino acids contributing to cold stability in Flaveria brownii C(4)-PPDK. The maintenance of PPDK and Rubisco large subunit amounts in M. x giganteus is consistent with the hypothesis that these proteins are critical to maintaining high rates of C(4) photosynthesis at low temperature.

Adaptation, Physiological↗

PubMed2003

Conserved noncoding sequences among cultivated cereal genomes identify candidate regulatory sequence elements and patterns of promoter evolution.

Surveys for conserved noncoding sequences (CNS) among genes from monocot cereal species were conducted to assess the general properties of CNS in grass genomes and their correlation with known promoter regulatory elements. Initial comparisons of 11 orthologous maize-rice gene pairs found that previously defined regulatory motifs could be identified within short CNS but could not be distinguished reliably from random sequence matches. Among the different phylogenetic footprinting algorithms tested, the VISTA tool yielded the most informative alignments of noncoding sequence. VISTA was used to survey for CNS among all publicly available genomic sequences from maize, rice, wheat, barley, and sorghum, representing >300 gene comparisons. Comparisons of orthologous maize-rice and maize-sorghum gene pairs identified 20 bp as a minimal length criterion for a significant CNS among grass genes, with few such CNS found to be conserved across rice, maize, sorghum, and barley. The frequency and length of cereal CNS as well as nucleotide substitution rates within CNS were consistent with the known phylogenetic distances among the species compared. The implications of these findings for the evolution of cereal gene promoter sequences and the utility of using the nearly completed rice genome sequence to predict candidate regulatory elements in other cereal genes by phylogenetic footprinting are discussed.

Algorithms↗

PubMed2002

Tandemly duplicated Safener-induced glutathione S-transferase genes from Triticum tauschii contribute to genome- and organ-specific expression in hexaploid wheat.

Glutathione S-transferase (GST) gene expression was examined in several Triticum species, differing in genome constitution and ploidy level, to determine genome contribution to GST expression in cultivated, hexaploid bread wheat (Triticum aestivum). Two tandemly duplicated tau class GST genes (TtGSTU1 and TtGSTU2) were isolated from a single bacterial artificial chromosome clone in a library constructed from the diploid wheat and D genome progenitor to cultivated wheat, Triticum tauschii. The genes are very similar in genomic structure and their encoded proteins are 95% identical. Gene-specific reverse transcriptase-polymerase chain reaction analysis revealed differential transcript accumulation of TtGSTU1 and TtGSTU2 in roots and shoots. Expression of both genes was induced by herbicide safeners, 2,4-dichlorophenoxyacetic acid and abscisic acid, in the shoots of T. tauschii; however, expression of TtGSTU1 was always higher than TtGSTU2. In untreated seedlings, TtGSTU1 was expressed in both shoots and roots, whereas TtGSTU2 expression was only detected in roots. RNA gel-blot analysis of ditelosomic, aneuploid lines that are deficient for 6AS, 6BS, or 6DS chromosome arms of cultivated, hexaploid bread wheat showed differential genome contribution to safener-induced GST expression in shoots compared with roots. The GST genes from the D genome of hexaploid wheat contribute most to safener-induced expression in the shoots, whereas GSTs from the B and D genomes contribute to safener-induced expression in the roots.

2,4-Dichlorophenoxyacetic Acid↗