Antisense inhibition of tomato fruit sucrose synthase decreases fruit setting and the sucrose unloading capacity of young fruit.
(57/2576)
The role of sucrose synthase (SuSy) in tomato fruit was studied in transgenic tomato (Lycopersicon esculentum) plants expressing an antisense fragment of fruit-specific SuSy RNA (TOMSSF) under the control of the cauliflower mosaic virus 35S promoter. Constitutive expression of the antisense RNA markedly inhibited SuSy activity in flowers and fruit pericarp tissues. However, inhibition was only slight in the endosperm and was undetectable in the embryo, shoot, petiole, and leaf tissues. The activity of sucrose phosphate synthase decreased in parallel with that of SuSy, but acid invertase activity did not increase in response to the reduced SuSy activity. The only effect on the carbohydrate content of young fruit was a slight reduction in starch accumulation. The in vitro sucrose import capacity of fruits was not reduced by SuSy inhibition at 23 days after anthesis, and the rate of starch synthesized from the imported sucrose was not lessened even when SuSy activity was decreased by 98%. However, the sucrose unloading capacity of 7-day-old fruit was substantially decreased in lines with low SuSy activity. In addition, the SuSy antisense fruit from the first week of flowering had a slower growth rate. A reduced fruit set, leading to markedly less fruit per plant at maturity, was observed for the plants with the least SuSy activity. These results suggest that SuSy participates in the control of sucrose import capacity of young tomato fruit, which is a determinant for fruit set and development. (+info)
Vacuolar H(+)-ATPase is expressed in response to gibberellin during tomato seed germination.
(58/2576)
Completion of germination (radicle emergence) by gibberellin (GA)-deficient (gib-1) mutant tomato (Lycopersicon esculentum Mill.) seeds is dependent upon exogenous GA, because weakening of the endosperm tissue enclosing the radicle tip requires GA. To investigate genes that may be involved in endosperm weakening or embryo growth, differential cDNA display was used to identify mRNAs differentially expressed in gib-1 seeds imbibed in the presence or absence of GA(4+7). Among these was a GA-responsive mRNA encoding the 16-kD hydrophobic subunit c of the V(0) membrane sector of vacuolar H(+)-translocating ATPases (V-ATPase), which we termed LVA-P1. LVA-P1 mRNA expression in gib-1 seeds was dependent on GA and was particularly abundant in the micropylar region prior to radicle emergence. Both GA dependence and tissue localization of LVA-P1 mRNA expression were confirmed directly in individual gib-1 seeds using tissue printing. LVA-P1 mRNA was also expressed in wild-type seeds during development and germination, independent of exogenous GA. Specific antisera detected protein subunits A and B of the cytoplasmic V(1) sector of the V-ATPase holoenzyme complex in gib-1 seeds only in the presence of GA, and expression was localized to the micropylar region. The results suggest that V-ATPase plays a role in GA-regulated germination of tomato seeds. (+info)
The gene distribution in the genomes of pea, tomato and date palm.
(59/2576)
The vast majority of genes of maize, rice, barley and wheat are contained in long gene-rich regions (collectively called the 'gene space') separated by long gene-empty regions. The gene space covers a narrow, 0.8-1.6%, GC range, possibly because of the presence of abundant transposons. Here we report that the gene space is not an exclusive property of Gramineae, because it also exists in the large genome of pea (5000 Mb). Moreover, the gene space is not just dependent upon genome size, since a gene space is found in rice (415 Mb), but not in Arabidopsis (120 Mb), nor in two other plants investigated in the present work, date palm (250 Mb) and tomato (1000 Mb). (+info)
The major site of the pti1 kinase phosphorylated by the pto kinase is located in the activation domain and is required for pto-pti1 physical interaction.
(60/2576)
The Pto and Pti1 serine/threonine protein kinases are key components of the signaling pathway leading to speck disease resistance in tomato. The two kinases physically interact in the yeast two-hybrid system, and Pto specifically phosphorylates Pti1 in vitro. In this study, we identified and characterized the major Pti1 site phosphorylated by Pto. Pto was expressed in Escherichia coli as a maltose-binding fusion protein (MBP-Pto), and used to phosphorylate in vitro a kinase deficient Pti1 protein fused to glutathione S-transferase (GST-Pti1[K96N]). The major phosphopeptide derived from trypsin digestion of phosphorylated GST-Pti1(K96N) was partially purified by reverse-phase HPLC and analyzed by matrix assisted laser desorption/ionization mass spectrometry. Its mass corresponded to phosphopeptide LHSTR, which lies in the Pti1 kinase activation domain at amino acid position 230-234. By phosphoamino acid analysis, Thr233 was determined to be the phosphorylation site of peptide LHSTR. Mutations of Thr233 reduced dramatically Pti1 phosphorylation by MBP-Pto and Pti1 autophosphorylation, providing evidence that the same Pti1 site is involved in the two reactions. Moreover, phosphorylation of Thr233 appeared to be required for Pto-Pti1 physical interaction, as a mutation of this site to alanine, but not to aspartate, abolished the interaction between Pto and Pti1 in the yeast two-hybrid system. (+info)
Characterization of P69E and P69F, two differentially regulated genes encoding new members of the subtilisin-like proteinase family from tomato plants.
(61/2576)
Subtilisin-like proteins represent an ancient family of serine proteases that are extremely widespread in living organisms. We report here the structure and genomic organization of two new transcriptionally active genes encoding proteins that belong to the P69 family of subtilisin-like proteases from tomato (Lycopersicon esculentum) plants. The two new members, P69E and P69F, are organized in a cluster and arranged in a tandem form. mRNA expression analysis and studies of transgenic Arabidopsis plants transformed with promoter-beta-glucuronidase fusions for each of these two genes revealed that they are differentially regulated, with each showing a highly specific mRNA expression pattern. P69E mRNA is expressed only in roots, while P69F mRNA is expressed only in hydathodes. A comparison of all the P69 amino acid sequences, gene structure, expression profiles, and clustered organization suggests a working model for P69 gene family evolution. (+info)
A putative role for the tomato genes DUMPY and CURL-3 in brassinosteroid biosynthesis and response.
(62/2576)
The dumpy (dpy) mutant of tomato (Lycopersicon esculentum Mill.) exhibits short stature, reduced axillary branching, and altered leaf morphology. Application of brassinolide and castasterone rescued the dpy phenotype, as did C-23-hydroxylated, 6-deoxo intermediates of brassinolide biosynthesis. The brassinolide precursors campesterol, campestanol, and 6-deoxocathasterone failed to rescue, suggesting that dpy may be affected in the conversion of 6-deoxocathasterone to 6-deoxoteasterone, similar to the Arabidopsis constitutive photomorphogenesis and dwarfism (cpd) mutant. Measurements of endogenous brassinosteroid levels by gas chromatography-mass spectrometry were consistent with this hypothesis. To examine brassinosteroid-regulated gene expression in dpy, we performed cDNA subtractive hybridization and isolated a novel xyloglucan endotransglycosylase that is regulated by brassinosteroid treatment. The curl-3 (cu-3) mutant (Lycopersicon pimpinellifolium inverted question markJusl. Mill.) shows extreme dwarfism, altered leaf morphology, de-etiolation, and reduced fertility, all strikingly similar to the Arabidopsis mutant brassinosteroid insensitive 1 (bri1). Primary root elongation of wild-type L. pimpinellifolium seedlings was strongly inhibited by brassinosteroid application, while cu-3 mutant roots were able to elongate at the same brassinosteroid concentration. Moreover, cu-3 mutants retained sensitivity to indole-3-acetic acid, cytokinins, gibberellin, and abscisic acid while showing hypersensitivity to 2, 4-dichlorophenoxyacetic acid in the root elongation assay. The cu-3 root response to hormones, coupled with its bri1-like phenotype, suggests that cu-3 may also be brassinosteroid insensitive. (+info)
A minimum length of N gene sequence in transgenic plants is required for RNA-mediated tospovirus resistance.
(63/2576)
We showed previously that transgenic plants with the green fluorescent protein (GFP) gene fused to segments of the nucleocapsid (N) gene of tomato spotted wilt virus (TSWV) displayed post-transcriptional gene silencing of the GFP and N gene segments and resistance to TSWV. These results suggested that a chimeric transgene composed of viral gene segments might confer multiple virus resistance in transgenic plants. To test this hypothesis and to determine the minimum length of the N gene that could trans-inactivate the challenging TSWV, transgenic plants were developed that contained GFP fused with N gene segments of 24-453 bp. Progeny from these plants were challenged with: (i) a chimeric tobacco mosaic virus containing the GFP gene, (ii) a chimeric tobacco mosaic virus with GFP plus the N gene of TSWV and (iii) TSWV. A number of transgenic plants expressing the transgene with GFP fused to N gene segments from 110 to 453 bp in size were resistant to these viruses. Resistant plants exhibited post-transcriptional gene silencing. In contrast, all transgenic lines with transgenes consisting of GFP fused to N gene segments of 24 or 59 bp were susceptible to TSWV, even though the transgene was post-transcriptionally silenced. Thus, virus resistance and post-transcriptional gene silencing were uncoupled when the N gene segment was 59 bp or less. These results provide evidence that multiple virus resistance is possible through the simple strategy of linking viral gene segments to a silencer DNA such as GFP. (+info)
Prostate cancer and dietary carotenoids.
(64/2576)
This population-based case-control study investigated associations between prostate cancer risk and dietary intake of the carotenoids beta-carotene and lycopene and their major plant food sources, including carrots, green leafy vegetables, and tomato-based foods. The study was carried out in Auckland, New Zealand, during 1996-1997 and recruited 317 prostate cancer cases and 480 controls. The authors found that dietary intake of beta-carotene and its main vegetable sources was largely unassociated with prostate cancer risk, whereas intake of lycopene and tomato-based foods was weakly associated with a reduced risk. These results suggest that in contrast to the findings regarding many types of cancers, vegetables rich in beta-carotene are not protective against prostate cancer. However, lycopene from tomato-based foods was found to be associated with a small reduction in risk. (+info)