rbcS Gene Family Research Articles

Cell-Specific Expression of Rubisco Small Subunit and Rubisco Activase Genes in C3 and C4 Species of Atriplex

In situ hybridisation techniques have been used to determine the distribution of mRNAs for ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco: EC 4.1.1.39) and Rubisco activase in leaves of Atriplex patula L. (C3) and A. rosea L. (C4). In A. patula, mRNA for Rubisco small subunit (encoded by the rbcS gene family) was found to accumulate in the mesophyll and bundle sheath, while in A. rosea it accumulated in the bundle sheath only, as shown previously for the C4 monocot Zea mays L. The spatial distribution of rca transcripts for Rubisco activase paralleled that for the rbcS transcripts in both C3 and C4 Atriplex species, providing evidence that Rubisco activase is required in cells only where Rubisco is present.

Expression dynamics of the tomato rbcS gene family during development.

The tomato rbcS gene family is composed of five genes (rbcS1, 2, 3A, 3B, and 3C) that are differentially expressed during tomato development. Nuclear run-on transcription assays and RNA analysis were used to determine the contribution of transcriptional and post-transcriptional regulation to the accumulation of mRNA from the five rbcS genes in tomato seedlings, leaves, and fruit. We found that the qualitative pattern of mRNA accumulation is regulated at the transcriptional level and that, in general, there is a correlation of rates of rbcS transcription with overall rbcS mRNA abundance in fruit and leaves. Although transcriptional control is a primary determinant for rbcS gene expression in tomato, examination of relative transcription rates and mRNA accumulation of each rbcS gene demonstrated that there is also significant post-transcriptional control of rbcS gene expression during organ development. Individual rbcS mRNAs, which have highly conserved coding sequences and differ only in their 5' and 3' untranslated sequences, have different stabilities. We showed that both transcription and stability of individual rbcS mRNAs are altered in different organs and by the developmental program within these organs as well as by exposure to light. Together, the results provide a comprehensive analysis of the extent of transcriptional and post-transcriptional control that operates within the rbcS gene family during plant development.

Developmental and Organ-Specific Changes in Promoter DNA-Protein Interactions in the Tomato rbcS Gene Family

Developmental and Organ-Specific Changes in Promoter DNA-Protein Interactions in the Tomato rbcS Gene Family

Developmental and organ-specific changes in promoter DNA-protein interactions in the tomato rbcS gene family.

The five genes encoding ribulose-1,5-bisphosphate carboxylase (rbcS) from tomato are differentially expressed. Transcription of the genes is organ specific and developmentally regulated in fruit and light regulated in cotyledons and leaves. DNase I footprinting assays were used to map multiple sites of DNA-protein interaction in the promoter regions of all five genes and to determine whether the differential transcriptional activity of each gene correlated with developmental or organ-specific changes in DNA-protein interactions. We show organ-specific differences in DNase I protection patterns, suggesting that differential transcription of rbcS genes is controlled at least in part at the level of DNA-protein interactions. In contrast, no changes were detected in the DNase I footprint pattern generated with nuclear extracts from dark-grown cotyledons versus cotyledons exposed to light, implying that light-dependent regulation of rbcS transcription is controlled by protein-protein interactions or modification of DNA binding proteins. During development of tomato fruit, most DNA-protein interactions in the rbcS promoter regions disappear, coincident with the transcriptional inactivation of the rbcS genes. In nuclear extracts from nonphotosynthetic roots and red fruit, the only detectable DNase I protection corresponds to a G-box binding activity. Detection of other DNA binding proteins in extracts from these organs and expression of nonphotosynthetic genes exclude the possibility that roots and red fruit are transcriptionally inactive. The absence of complex promoter protection patterns in these organs suggests either that cooperative interactions between different DNA binding proteins are necessary to form functional transcription complexes or that there is developmental and organ-specific regulation of several rbcS-specific transcription factors in these organs. The DNase I-protected DNA sequences defined in this study are discussed in the context of conserved DNA sequence motifs and previously characterized binding sites.

Chloroplast and Nuclear Transcripts for Plastid Proteins in Arabidopsis thaliana: Tissue Distribution in Mature Plants and During Seedling Development and Embryogenesis

AbstractWe have investigated the distribution of transcripts for chloroplast proteins involved in photosynthesis and carbon assimilation in Arabidopsis thaliana. The probes that were used for assessment of transcripts represent the chloroplast genes psbA (encoding the D1 protein of photosystem II) and rbcL (for the large subunit of RubisCO) as well as the nuclear rbcS gene family for the RubisCO small subunit. With any of these probes we find a tissue‐specific distribution of transcripts in mature plants, with the highest concentration in rosette leaves and almost undetectable amounts in roots. The transcripts detected by each of these probes reveal similar spatial distribution and temporal kinetics during seedling development, with maximal levels around 70 h after sowing. They each show higher levels under light‐grown as compared to dark‐grown conditions, indicating a coarse control that ensures roughly coordinated levels throughout plastid differentiation. Embryonic transcripts are present in much higher concentration within the ground meristem and protoderm than in the procambium, which seems to reflect the different degree of determination towards the subsequent function in photosynthesis. Transcripts were detected in all characteristic stages throughout embryogenesis including the (non‐green) proembryo stage, suggesting that chlorophyll accumulation is not essential for expression of these genes at the RNA level. Both processes, hence, appear to be triggered by earlier molecular events that remain to be characterized.

Expression Dynamics of the Tomato rbcS Gene Family during Development

Expression Dynamics of the Tomato rbcS Gene Family during Development

Reduced steady-state levels of rbcS mRNA in plants kept in the dark are due to differential degradation.

When plants are placed in the dark, the level of the abundant mRNA encoding the small subunit of ribulose-1,5-bisphosphate carboxylase (rbcS) declines rapidly. We present evidence demonstrating an active degradation of rbcS mRNA in the dark. Detailed analysis shows that transcripts originating from different members of the rbcS gene family are differentially affected by this degradation. This phenomenon is not common to all light-regulated plant genes since the mRNA for ST-LS1, another leaf-specific and light-induced gene, is not degraded in the dark within the same time scale.

Abscisic Acid Control of rbcS and cab Transcription in Tomato Leaves

Leaves of tomato (Lycopersicon esculentum) plants grown in soil in which moisture was lowered from field capacity to levels approaching permanent wilting point show a 10-fold increase in abscisic acid (ABA) and a 60 to 70 percent decrease in rbcS and cab steady-state mRNA levels. As indicated by transcription run-on experiments, the effect occurs primarily at the transcriptional level. Similar water deficit had only a minor effect on ABA level and on rbcS and cab expression in leaves of sitiens, an ABA mutant of tomato. Expression of rbcL, the chloroplast gene coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, is not affected by water stress. Application of exogenous ABA results in decreased rbcS and cab expression in both wild-type and sitiens leaves. Analysis of the expression of individual members of the rbcS gene family indicates that under water-deficit conditions, expression derives primarily from only three of the five rbcS genes. Effects of dark adaptation and water deficit are additive for cab but not for rbcS expression. These results support the hypothesis that, at least under water-deficit conditions, ABA or a derivative thereof mediates a negative regulation of rbcS and cab transcription in tomato plants.

Maturation in Larch

The effect of maturation on the morphological and photosynthetic characteristics, as well as the expression of two genes involved in photosynthesis in the developing, current year foliage of Eastern larch (Larix laricina [Du Roi]) is described. These effects were observed on foliage during the third growing season after grafting of scions from trees of different ages onto 2 year old rootstock. Specific leaf weight (gram dry weight per square meter), leaf cross-sectional area (per square millimeter), and chlorophyll content (milligram per gram dry weight) all increase with increasing age in long shoot foliage from both indoor- and outdoor-grown trees. Net photosynthesis (NPS) (mole of CO(2) per square millimeter per second) increases with age on indoor- but not outdoor-grown trees. NPS also increases with increased chlorophyll content, but outdoor-grown scions of all ages had higher chlorophyll content, and chlorophyll does not appear to be limiting for NPS outdoors. To extend these studies of maturation-related differences in foliar morphology and physiology to the molecular genetic level, sequences were cloned from the cab and rbsS gene families of larch. Both cab and rbcS gene families are expressed in foliage but not in roots, and they are expressed in light-grown seedlings of larch but only at very low levels in dark-grown seedlings (~2% of light-grown seedlings). Steady-state cab mRNA levels are relatively higher (~40%) in newly expanding short shoot foliage from juvenile plants compared to mature plants. Unlike cab, the expression of the rbcS gene family did not seem to vary with age. These data show that the maturation-related changes in morphological and physiological phenotypes are associated with changes in gene expression. No causal relationship has been established, however. Indeed, we conclude that the faster growth of juvenile scions reported previously (MS Greenwood, CA Hopper, KW Hutchison [1989] Plant Physiol 90: 406-412) is not due to increased NPS or cab expression. Long shoot foliage is the dominant foliar type on young trees and its lower specific leaf weight will permit production of more photosynthetic surface area per unit of leaf biomass.

Sequence Characteristics and Transcripts of rbcS Genes from Brassica napus: Temporal and Spatial Expression During Crucifer Seedling Morphogenesis*

AbstractThe small subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase is encoded by a nuclear multigene family (rbcS genes). We have cloned and characterized three rbcS cDNA sequences from Brassica napus. These cDNA clones all appear to encode the same protein, but they differ in their nucleotide sequence, which has been exploited in the construction of clone‐specific oligonucleotides as selective hybridization probes. By using a nonselective RNA probe, the temporal expression of the entire rbcS gene family was analyzed during seedling development of Brassica napus and of Sinapis alba. In both crucifer species, rbcS transcripts show transient peak levels and then decrease, although to a different degree. Only a moderate (twofold) difference in transcript pool sizes is observed in light‐grown versus dark‐grown seedlings at the time of peak levels, while a much higher light/dark ratio is found in late‐stage seedlings. The oligonucleotide probes reveal three subsets of transcripts which differ in their accumulation kinetics and light/dark ratio. Assessment of the spatial distribution by using in situ hybridization indicates that rbcS transcripts are uniformly localized in cross‐sections of cotyledons from either light‐grown or dark‐grown seedlings, whereas they are undetectable in root sections.

RbcS genes in Solanum tuberosum: conservation of transit peptide and exon shuffling during evolution.

Five genes of the rbcS gene family of Solanum tuberosum (potato) were studied. One of these is a cDNA clone; the other four are located on two genomic clones representing two different chromosomal loci containing one (locus 1) and three genes (locus 2), respectively. The intron/exon structure of the three genes in locus 2 is highly conserved with respect to size and position. These genes contain two introns, whereas the gene from locus 1 contains three introns. Although in most cases the amino acid sequences in the transit peptide part of different rbcS genes from the same species varied considerably more than the corresponding mature amino acid sequences, one exception found in tomato and potato indicates that the transit peptide of rbcS could have a special function. A comparison of the rbcS genes of higher plants with those of prokaryotes offers suggestive evidence that introns first served as spacer material in the process of exon shuffling and then were removed stepwise during the evolution of higher plants.

Organization and expression of the genes encoding ribulose-1,5-bisphosphate carboxylase in higher plants

The chloroplast gene encoding the large subunit (rbcL) and the nuclear multigene family encoding the small subunit (rbcS) of ribulose-1,5-bisphosphate carboxylase have been extensively studied in several higher plants. Comparisons among the characterized genes at the structural and organizational levels, as well as at the level of gene expression and regulation, show evolutionarily conserved and divergent features. Individual members of the rbcS gene families of tomato, petunia, and pea are differentially expressed, and show developmental, organ-specific, and light regulation depending upon the species examined. Upstream nucleotide sequences from rbcS genes of several dicotyledonous plants were aligned in order to identify those sequences which may be important in regulating rbcS expression.

Nucleotide sequence and molecular evolution of two tomato genes encoding the small subunit of ribulose-1,5-bisphosphate carboxylase

We have isolated and sequenced two cDNA clones (LESS5 and LESS17) encoding the small subunit of ribulose-1,5-bisphosphate carboxylase of tomato ( Lycopersicon esculentum). At the nucleotide level, the protein-coding regions of these genes are 85% conserved, while the untranslated 3' regions are only 55% conserved. Comparison with rbcS genes from other species of Solanaceae suggests that the tomato LESS5 gene, the Nicotiana tabacum NTSS23 gene and the Petunia hybrida SSU8 gene are orthologous members of the rbcS gene family. In addition, the tomato gene LESS17, and the Petunia hybrida gene SSU611, may also be orthologous, since their untranslated 3' regions are related. There is a large difference between the two tomato rbcS genes in the frequency of the CG dinucleotide. This difference may reflect different levels of methylation, and therefore expression, of the tomato genes. Many of the differences involving the CG dinucleotide can be represented as transitions between C and T on the noncoding strand. Such changes are consistent with observations that methylated cytosines are hot-spots for transitions.