Cláudia Regina Batista de Souza

Recent Molecular Advances on Downstream Plant Responses to Abiotic Stress

Abiotic stresses such as extremes of temperature and pH, high salinity and drought, comprise some of the major factors causing extensive losses to crop production worldwide. Understanding how plants respond and adapt at cellular and molecular levels to continuous environmental changes is a pre-requisite for the generation of resistant or tolerant plants to abiotic stresses. In this review we aimed to present the recent advances on mechanisms of downstream plant responses to abiotic stresses and the use of stress-related genes in the development of genetically engineered crops.

Comparative gene expression study to identify genes possibly related to storage root formation in cassava.

Cassava storage roots result from swelling of adventitious roots by secondary growth. In the present study we aimed to gain insight into the molecular processes occurring during cassava storage root formation. We report a comparative gene expression study in adventitious and storage roots in order to identify genes possibly related to storage organ formation. Our results revealed five genes with higher expression levels in secondary xylem of storage roots than adventitious roots. Among them, the Mec1 gene coding for Pt2L4 glutamic acid-rich protein and a putative RING Zinc Finger and LEA protein genes were strongly induced in secondary xylem tissue.

Characterization of Carotenoid-protein Complexes and Gene Expression Analysis Associated with Carotenoid Sequestration in Pigmented Cassava (Manihot Esculenta Crantz) Storage Root.

Carotenoid-protein complex (CPC) was isolated from chromoplast-enriched suspensions of cassava storage root (CSR) using size exclusion chromatography and characterized. Peptide sequences (LC_MS/MS spectrum) obtained from CPC and their corresponding proteins were obtained using publically available databases. Small Heat Shock Proteins (sHSPs) were the most abundant proteins identified in the CPC. Western blot analysis showed that Fribrillin and Or-protein were present in chromoplast-enriched suspensions of yellow root but not in the complex or white root. Results from qRT-PCR helped identify an isoform of HSP21 possessing four single point mutations in the intense yellow CSR that may be responsible for increased sequestration of b-carotene.

Evidence for a novel biological role for the multifunctional β-1,3-glucan binding protein in shrimp.

β-1,3-Glucan binding proteins (βGBPs) are soluble pattern recognition proteins/receptors that bind to β-1,3-glucans from fungi cell walls. In crustaceans, βGBPs are abundant plasmatic proteins produced by the hepatopancreas, and have been proved to play multiple biological functions. Here, we purified and characterized novel members of the βGBP family from the hemolymph of two Brazilian shrimps, Farfantepenaeus paulensis (FpβGBP) and Litopenaeus schmitti (LsβGBP). As observed for other crustacean species, FpβGBP and LsβGBP are monomeric proteins (∼100kDa) able to enhance the activation of the prophenoloxidase system, a potent antimicrobial defense conserved in arthropods. More interestingly, we provided here evidence for a novel biological activity for shrimp βGBPs: the agglutination of fungal cells. Finally, we investigated the modulation of the βGBP gene in F. paulensis shrimps experimentally infected with a cognate fungal pathogen, Fusarium solani. From our expression data, βGBP gene is constitutively expressed in hepatopancreas and not modulated upon a non-lethal fungal infection. Herein, we have improved our knowledge about the βGBP family by the characterization of a novel biological role for this multifunctional protein in shrimp.

A cDNA Sequence Coding for a Glutamic Acid-Rich Protein Is Differentially Expressed in Cassava Storage Roots

We report the isolation and characterization of a cDNA sequence (Mec1) coding for a glutamic acid-rich protein (Pt2L4) from cassava storage roots. Comparative sequence analysis showed a high identity of Pt2L4 with cassava protein C54, which is expressed in vascular tissues of storage roots. Northern blot analysis showed that the Mec1 transcript expression pattern might be related to the maturation of the storage parenchyma cells.

Phytocystatins and their Potential to Control Plant Diseases Caused by Fungi

Plant cystatins, also called phytocystatins, constitute a family of specific cysteine protease inhibitors found in several monocots and dicots, where they can be involved in the regulation of several endogenous processes and in defense against pests and pathogens, as well as in response to abiotic stress. In this mini-review we aimed to present isolated and characterized phytocystatins with potential use in control of plant disease caused by fungi.

Molecular cloning and characterization of a novel RING zinc-finger protein gene up-regulated under in vitro salt stress in cassava

Cassava (Manihot esculenta Crantz) is one of the world’s most important food crops. It is cultivated mainly in developing countries of tropics, since its root is a major source of calories for low-income people due to its high productivity and resistance to many abiotic and biotic factors. A previous study has identified a partial cDNA sequence coding for a putative RING zinc finger in cassava storage root. The RING zinc finger protein is a specialized type of zinc finger protein found in many organisms. Here, we isolated the full-length cDNA sequence coding for M. esculenta RZF (MeRZF) protein by a combination of 5′ and 3′ RACE assays. BLAST analysis showed that its deduced amino acid sequence has a high level of similarity to plant proteins of RZF family. MeRZF protein contains a signature sequence motif for a RING zinc finger at its C-terminal region. In addition, this protein showed a histidine residue at the fifth coordination site, likely belonging to the RING-H2 subgroup, as confirmed by our phylogenetic analysis. There is also a transmembrane domain in its N-terminal region. Finally, semi-quantitative RT-PCR assays showed that MeRZF expression is increased in detached leaves treated with sodium chloride. Here, we report the first evidence of a RING zinc finger gene of cassava showing potential role in response to salt stress.

Identifying Sequences Potentially Related to Resistance Response of Piper tuberculatum to Fusarium solani f. sp. piperis by Suppression Subtractive Hybridization

Piper tuberculatum is an exotic Piper from the Amazon region that shows resistance to infection by Fusarium solani f. sp. piperis, causal agent of Fusarium disease in black pepper (Piper nigrum L.). In this work we aimed to study the interaction between P. tuberculatum and F. solani f. sp. piperis at a molecular level, using suppression subtractive hybridization to identify genes potentially related to Fusarium disease resistance. Comparative sequence analysis confirmed that clones isolated here show a high identity with genes coding for proteins that have a known role in plant defense response mechanisms, such as peroxidase, hydroxyproline-rich glycoprotein and CBL-interacting protein kinase. The present study constitutes the first effort to understand the molecular basis of this plant-pathogen interaction, identifying genes which may be used in the future genetic improvement of black pepper.

Identification of sequences expressed during compatible black pepper—Fusarium solani f. sp. piperis interaction

Black pepper (Piper nigrum L.) is one of the most widely used spices in the world. Root rot disease is induced by Fusarium solani f. sp. piperis and causes severe yield losses of this crop in the Amazon region. In this work we used the suppression subtractive hybridization to identify differentially expressed sequences in roots of black pepper infected by F. solani f. sp. piperis. Sequences coding for putative proteins related to oxidative burst and defense response, such as superoxide dismutase, cytochrome p450, and alpha-amylase inhibitors/lipid transfer protein, comprised 28.4% of SSH clones according to computational analyses. Furthermore, semi-quantitative RT-PCR assays showed accumulation of putative cysteine proteinase inhibitor and pathogenesis-related protein 4 transcripts at late stage of infection that can help to explain the success of this pathogen in causing root rot disease in black pepper. The results obtained here contribute to improve our understanding about this plant–pathogen interaction.

Pt2L4 Protein, a Homologue to Hev b 5 from Rubber Tree, May Not Be Responsible for the Cross-Reactions to Cassava Show by People Allergic to Latex

Pt2L4 is a protein from cassava homologue to Hevb5, a principal allergen from latex. Here we aimed to elucidate immunological relationships between these proteins. Our results revealed that epitopes found in Hev b 5 are not entirely conserved in Pt2L4 which is not recognized by IgE from patients allergic to Hev b 5.