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1.
Plant Biotechnol J ; 8(3): 263-76, 2010 Apr.
Article in English | MEDLINE | ID: mdl-20388126

ABSTRACT

An increasing number of plant scientists, including breeders, agronomists, physiologists and molecular biologists, are working towards the development of new and improved energy crops. Research is increasingly focused on how to design crops specifically for bioenergy production and increased biomass generation for biofuel purposes. The most important biofuel to date is bioethanol produced from sugars (sucrose and starch). Second generation bioethanol is also being targeted for studies to allow the use of the cell wall (lignocellulose) as a source of carbon. If a crop is to be used for bioenergy production, the crop should be high yielding, fast growing, low lignin content and requiring relatively small energy inputs for its growth and harvest. Obtaining high yields in nonprime agricultural land is a key for energy crop development to allow sustainability and avoid competition with food production. Sugarcane is the most efficient bioenergy crop of tropical and subtropical regions, and biotechnological tools for the improvement of this crop are advancing rapidly. We focus this review on the studies of sugarcane genes associated with sucrose content, biomass and cell wall metabolism and the preliminary physiological characterization of cultivars that contrast for sugar and biomass yield.


Subject(s)
Biofuels , Saccharum/genetics , Saccharum/metabolism , Sucrose/metabolism , Biomass , Breeding , Cell Wall/metabolism , Crops, Agricultural/chemistry , Crops, Agricultural/genetics , Crops, Agricultural/growth & development , Saccharum/growth & development
2.
BMC Genomics ; 10: 120, 2009 Mar 21.
Article in English | MEDLINE | ID: mdl-19302712

ABSTRACT

BACKGROUND: Sucrose content is a highly desirable trait in sugarcane as the worldwide demand for cost-effective biofuels surges. Sugarcane cultivars differ in their capacity to accumulate sucrose and breeding programs routinely perform crosses to identify genotypes able to produce more sucrose. Sucrose content in the mature internodes reach around 20% of the culms dry weight. Genotypes in the populations reflect their genetic program and may display contrasting growth, development, and physiology, all of which affect carbohydrate metabolism. Few studies have profiled gene expression related to sugarcane's sugar content. The identification of signal transduction components and transcription factors that might regulate sugar accumulation is highly desirable if we are to improve this characteristic of sugarcane plants. RESULTS: We have evaluated thirty genotypes that have different Brix (sugar) levels and identified genes differentially expressed in internodes using cDNA microarrays. These genes were compared to existing gene expression data for sugarcane plants subjected to diverse stress and hormone treatments. The comparisons revealed a strong overlap between the drought and sucrose-content datasets and a limited overlap with ABA signaling. Genes associated with sucrose content were extensively validated by qRT-PCR, which highlighted several protein kinases and transcription factors that are likely to be regulators of sucrose accumulation. The data also indicate that aquaporins, as well as lignin biosynthesis and cell wall metabolism genes, are strongly related to sucrose accumulation. Moreover, sucrose-associated genes were shown to be directly responsive to short term sucrose stimuli, confirming their role in sugar-related pathways. CONCLUSION: Gene expression analysis of sugarcane populations contrasting for sucrose content indicated a possible overlap with drought and cell wall metabolism processes and suggested signaling and transcriptional regulators to be used as molecular markers in breeding programs. Transgenic research is necessary to further clarify the role of the genes and define targets useful for sugarcane improvement programs based on transgenic plants.


Subject(s)
Gene Expression Regulation, Plant/genetics , Genes, Plant/genetics , Saccharum/chemistry , Saccharum/genetics , Sucrose/analysis , Agriculture , Gene Expression Profiling , Genotype , Oligonucleotide Array Sequence Analysis , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/genetics , Transcription Factors/genetics
3.
Biochim Biophys Acta ; 1759(1-2): 89-98, 2006.
Article in English | MEDLINE | ID: mdl-16574256

ABSTRACT

The Glycine max sucrose binding protein (GmSBP2) promoter directs phloem-specific expression of reporter genes in transgenic tobacco. Here, we identified cis-regulatory domains (CRD) that contribute with positive and negative regulation for the tissue-specific pattern of the GmSPB2 promoter. Negative regulatory elements in the distal CRD-A (-2000 to -700) sequences suppressed expression from the GmSBP2 promoter in tissues other than seed tissues and vascular tissues of vegetative organs. Deletion of this region relieved repression resulting in a constitutive promoter highly active in all tissues analyzed. Further deletions from the strong constitutive -700GmSBP2 promoter delimited several intercalating enhancer-like and repressing domains that function in a context-dependent manner. Histochemical examination revealed that the CRD-C (-445 to -367) harbors both negative and positive elements. This region abolished promoter expression in roots and in all tissues of stems except for the inner phloem. In contrast, it restores root meristem expression when fused to the -132pSBP2-GUS construct, which contains root meristem expression-repressing determinants mapped to the 44-bp CRD-G (-136 to -92). Thus, the GmSBP2 promoter is functionally organized into a proximal region with the combinatorial modular configuration of plant promoters and a distal domain, which restricts gene expression to the vascular tissues in vegetative organs.


Subject(s)
Carrier Proteins/genetics , Enhancer Elements, Genetic , Gene Expression Regulation, Plant , Hypocotyl/cytology , Promoter Regions, Genetic , Animals , Genes, Plant , Hypocotyl/genetics , Plant Structures/genetics , Plants, Genetically Modified , Nicotiana
4.
Genes Dev ; 18(20): 2545-56, 2004 Oct 15.
Article in English | MEDLINE | ID: mdl-15489295

ABSTRACT

Despite the large number of leucine-rich-repeat (LRR) receptor-like-kinases (RLKs) in plants and their conceptual relevance in signaling events, functional information is restricted to a few family members. Here we describe the characterization of new LRR-RLK family members as virulence targets of the geminivirus nuclear shuttle protein (NSP). NSP interacts specifically with three LRR-RLKs, NIK1, NIK2, and NIK3, through an 80-amino acid region that encompasses the kinase active site and A-loop. We demonstrate that these NSP-interacting kinases (NIKs) are membrane-localized proteins with biochemical properties of signaling receptors. They behave as authentic kinase proteins that undergo autophosphorylation and can also phosphorylate exogenous substrates. Autophosphorylation occurs via an intermolecular event and oligomerization precedes the activation of the kinase. Binding of NSP to NIK inhibits its kinase activity in vitro, suggesting that NIK is involved in antiviral defense response. In support of this, infectivity assays showed a positive correlation between infection rate and loss of NIK1 and NIK3 function. Our data are consistent with a model in which NSP acts as a virulence factor to suppress NIK-mediated antiviral responses.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/virology , Geminiviridae/metabolism , Protein Kinases/metabolism , Signal Transduction , Viral Proteins/metabolism , Amino Acid Sequence , Arabidopsis Proteins/genetics , Binding Sites , Geminiviridae/pathogenicity , Membrane Proteins/metabolism , Microscopy, Fluorescence , Molecular Sequence Data , Phosphorylation , Protein Binding , Recombinant Fusion Proteins , Reverse Transcriptase Polymerase Chain Reaction , Sequence Alignment , Sequence Analysis, DNA , Two-Hybrid System Techniques , Viral Proteins/genetics , Virulence/genetics
5.
J Exp Bot ; 54(393): 2643-53, 2003 Dec.
Article in English | MEDLINE | ID: mdl-14585823

ABSTRACT

The sucrose binding protein (SBP) from soybean has been implicated as an important component of the sucrose uptake system. Two SBP genomic clones, gsS641.1 and gsS641.2, which correspond to allelic forms of the GmSBP2/S64 gene, have been isolated and characterized. As a member of the seed storage protein superfamily, it has been shown that the SBP gene structure is similar to vicilin genes with intron/exon boundaries at conserved positions. Fluores cence in situ hybridization (FISH) suggested that the soybean SBP gene family is represented by at least two non-allelic genes corresponding to the previously isolated GmSBP1 and GmSBP2/S64 cDNAs. These two cDNAs share extensive sequence similarity but are located at different loci in the soybean genome. To investigate transcriptional activation of the GmSBP2 gene, 2 kb 5'-flanking sequences of gsS641.1 and gsS641.2 were fused to the beta-glucuronidase (GUS) reporter gene and to the green fluorescent protein (GFP) reporter gene and inde pendently introduced into Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. The SBP2 promoter directed expression of both GUS and GFP reporter genes with high specificity to the phloem of leaves, stems and roots. Thus, the overall pattern of SBP-GUS or SBP-GFP expression is consistent with the involvement of SBP in sucrose translocation-dependent physiological processes.


Subject(s)
Carrier Proteins/genetics , Genes, Plant/genetics , Glycine max/genetics , Membrane Transport Proteins , Multigene Family , Plant Lectins/genetics , Soybean Proteins/genetics , Base Sequence , Gene Library , Genome, Plant , Molecular Sequence Data , Nucleic Acid Hybridization , Plants, Genetically Modified/genetics , Promoter Regions, Genetic/genetics , Restriction Mapping
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