Analysis of xyloglucan fucosylation in Arabidopsis.

Xyloglucan (XyG) is a load-bearing primary wall component in dicotyledonous and non-graminaceous monocotyledonous plants. XyG fucosyltransferase (FUTase), encoded by the Arabidopsis gene AtFUT1, directs addition of fucose (Fuc) residues to terminal galactose residues on XyG side chains. Reverse transcription-polymerase chain reaction and analysis of promoter-beta-glucuronidase transgenic plants indicated highest expression of AtFUT1 in the upper portion of elongating inflorescence stems of Arabidopsis.

Regulation of expansin gene expression affects growth and development in transgenic rice plants.

To investigate the in vivo functions of expansins, we generated transgenic rice plants that express sense and antisense constructs of the expansin gene OsEXP4. In adult plants with constitutive OsEXP4 expression, 12% of overexpressors were taller and 88% were shorter than the average control plants, and most overexpressors developed at least two additional leaves. Antisense plants were shorter and flowered earlier than the average control plants.

Evidence of mitochondrial involvement in the transduction of signals required for the induction of genes associated with pathogen attack and senescence.

Using the mRNA differential display technique, seven cDNAs have been isolated that are rapidly induced when cultured tobacco (Nicotiana tabacum) cells are treated with the mitochondrial electron transport inhibitor antimycin A (AA). Interestingly, six of the cDNAs show distinct similarity to genes known to be induced by processes that involve programmed cell death (PCD), such as senescence and pathogen attack. All of the cDNAs as well as Aox1, a gene encoding the alternative oxidase, were found to also be strongly induced by H2O2 and salicylic acid (SA).

Characterization of a family of Arabidopsis genes related to xyloglucan fucosyltransferase1.

To understand primary cell wall assembly in Arabidopsis, we have focused on identifying and characterizing enzymes involved in xyloglucan biosynthesis. Nine genes (AtFUT2-10) were identified that share between 47% and 62% amino acid similarity with the xyloglucan-specific fucosyltransferase AtFUT1. Reverse transcriptase-PCR analysis indicates that all these genes are expressed.

Microarray analysis of diurnal and circadian-regulated genes in Arabidopsis.

Plants respond to day/night cycling in a number of physiological ways. At the mRNA level, the expression of some genes changes during the 24-hr period. To identify novel genes regulated in this way, we used microarrays containing 11,521 Arabidopsis expressed sequence tags, representing an estimated 7800 unique genes, to determine gene expression levels at 6-hr intervals throughout the day.

AtVPS45 complex formation at the trans-Golgi network.

The Sec1p family of proteins are thought to be involved in the regulation of vesicle fusion reactions through interaction with t-SNAREs (target soluble N-ethylmaleimide-sensitive factor attachment protein receptors) at the target membrane. AtVPS45 is a member of this family from Arabidopsis thaliana that we now demonstrate to be present on the trans-Golgi network (TGN), where it colocalizes with the vacuolar cargo receptor AtELP. Unlike yeast Vps45p, AtVPS45 does not interact with, or colocalize with, the prevacuolar t-SNARE AtPEP12.

A novel gibberellin-induced gene from rice and its potential regulatory role in stem growth.

Os-GRF1 (Oryza sativa-GROWTH-REGULATING FACTOR1) was identified in a search for genes that are differentially expressed in the intercalary meristem of deepwater rice (Oryza sativa L.) internodes in response to gibberellin (GA). Os-GRF1 displays general features of transcription factors, contains a functional nuclear localization signal, and has three regions with similarities to sequences in the database.

The t-SNARE AtVAM3p resides on the prevacuolar compartment in Arabidopsis root cells.

Protein cargo is trafficked between the organelles of the endomembrane system inside transport vesicles, a process mediated by integral membrane proteins called SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) that reside on the surface of the vesicle (v-SNAREs) and target membrane (t-SNAREs). In examining transport of cargo between the trans-Golgi network and the vacuole in Arabidopsis, we have previously characterized AtPEP12p as a t-SNARE residing on the prevacuolar compartment and AtVTI1a as a v-SNARE that interacts with AtPEP12p. Recently, we have begun to characterize AtVAM3p, another Arabidopsis t-SNARE that shows high sequence homology to AtPEP12p.

GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts.

Protein import into chloroplasts is an energy-requiring process mediated by a proteinaceous import apparatus. Although previous work has shown that low levels of ATP or GTP can support precursor binding, the role of GTP during the import process remains unclear. Specifically, it is unknown whether GTP plays a separate role from ATP during the early stages of protein import and whether GTP has any role in the later stages of transport.

Xyloglucan fucosyltransferase, an enzyme involved in plant cell wall biosynthesis.

Cell walls are crucial for development, signal transduction, and disease resistance in plants. Cell walls are made of cellulose, hemicelluloses, and pectins. Xyloglucan (XG), the principal load-bearing hemicellulose of dicotyledonous plants, has a terminal fucosyl residue.

Expression of a gibberellin-induced leucine-rich repeat receptor-like protein kinase in deepwater rice and its interaction with kinase-associated protein phosphatase.

We identified in deepwater rice (Oryza sativa L.) a gene encoding a leucine-rich repeat receptor-like transmembrane protein kinase, OsTMK (O. sativa transmembrane kinase).

Feedback regulation of GA5 expression and metabolic engineering of gibberellin levels in Arabidopsis.

The gibberellin (GA) 20-oxidase encoded by the GA5 gene of Arabidopsis directs GA biosynthesis to active GAs, whereas that encoded by the P16 gene of pumpkin endosperm leads to biosynthesis of inactive GAs. Negative feedback regulation of GA5 expression was demonstrated in stems of Arabidopsis by bioactive GAs but not by inactive GA. In transgenic Arabidopsis plants overexpressing P16, there was a severe reduction in the amounts of C20-GA intermediates, accumulation of large amounts of inactive GA25 and GA17, a reduction in GA4 content, and a small increase in GA1.

A protein phosphatase 2C gene, LjNPP2C1, from Lotus japonicus induced during root nodule development.

Symbiotic interactions between legumes and compatible strains of rhizobia result in root nodule formation. This new plant organ provides the unique physiological environment required for symbiotic nitrogen fixation by the bacterial endosymbiont and assimilation of this nitrogen by the plant partner. We have isolated two related genes (LjNPP2C1 and LjPP2C2) from the model legume Lotus japonicus that encode protein phosphatase type 2C (PP2C).

The evolutionary origin of the protein-translocating channel of chloroplastic envelope membranes: identification of a cyanobacterial homolog.

The known envelope membrane proteins of the chloroplastic protein import apparatus lack sequence similarity to proteins of other eukaryotic or prokaryotic protein transport systems. However, we detected a putative homolog of the gene encoding Toc75, the protein-translocating channel from the outer envelope membrane of pea chloroplasts, in the genome of the cyanobacterium Synechocystis sp. PCC 6803.

Tissue localization of expansins in deepwater rice.

Expansins are a family of proteins capable of inducing stress relaxation of isolated cell walls. In earlier studies, we showed that the expression of expansin genes in deepwater rice (Oryza sativa L.) is regulated by developmental, hormonal and environmental stimuli.

Nodule parenchyma-specific expression of the sesbania rostrata early nodulin gene SrEnod2 is mediated by its 3' untranslated region.

The early nodulin Enod2 gene encodes a putative hydroxyproline-rich cell wall protein and is expressed exclusively in the nodule parenchyma cell layer. The latter finding suggests that the Enod2 protein may contribute to the special morphological features of the nodule parenchyma and to the creation of an oxygen diffusion barrier. The Enod2 gene of the stem-nodulating legume Sesbania rostrata (SrEnod2) is induced specifically in roots by the plant hormone cytokinin, and this induction occurs at a post-transcriptional level.

A putative vacuolar cargo receptor partially colocalizes with AtPEP12p on a prevacuolar compartment in Arabidopsis roots.

Targeting of protein cargo to the vacuole/lysosome is a multistep process that appears to have conserved features between mammalian, yeast, and plant cells. In each case, some soluble vacuolar/lysosomal proteins are believed to be bound by transmembrane cargo receptors in the trans-Golgi network (TGN) that redirect these proteins into clathrin-coated vesicles. These vesicles then appear to be transported to the prevacuole/endosome by a trafficking machinery that requires components identified in other vesicle-targeting steps such as N-ethylmaleimide-sensitive factor (NSF), soluble NSF attachment protein (SNAP), SNAP receptors (SNAREs), rab-type GTPases, and Sec1p homologs.

Direct evidence for rapid degradation of Bacillus thuringiensis toxin mRNA as a cause of poor expression in plants.

It is well established that the expression of Bacillus thuringiensis (B.t.) toxin genes in higher plants is severely limited at the mRNA level, but the cause remains controversial.

Premature polyadenylation at multiple sites within a Bacillus thuringiensis toxin gene-coding region.

Some foreign genes introduced into plants are poorly expressed, even when transcription is controlled by a strong promoter. Perhaps the best examples of this problem are the cry genes of Bacillus thuringiensis (B.t.

The Lotus japonicus LjNOD70 nodulin gene encodes a protein with similarities to transporters.

A novel nodule-specific gene, LjNOD70, associated with late stages in Lotus japonicus nodule development and/or functioning was characterized. The LjNOD70 gene is a member of a small family of closely related L. japonicus genes.

A gene encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase produces two transcripts: elucidation of a conserved response.

Indole-3-acetic acid (IAA) promotes ethylene biosynthesis in stems of etiolated pea (Pisum sativum L.) seedlings by rapidly increasing the expression of 1-aminocyclopropane-1-carboxylate (ACC) synthase mRNA and by enhancing the activity of the enzyme. Two cDNA clones encoding ACC synthase, Ps-ACS1 and Ps-ACS2, were isolated from a cDNA library prepared from the apical hooks of etiolated pea seedlings that had been treated with 100 microns IAA for 4 h.