Ribosome inactivating proteins purification from a medicinal plant

The ribosome inactivating proteins (RIPs) from plants possess RNA N- glycosidase activity that depurinates the major rRNA, thus damaging ribosomes in an irreversible manner and arresting protein synthesis. RIPs are presently classified as rRNA N-glycosidase in the enzyme nomenclature (EC 3.2.2.22) and do exhibit other enzymatic activities such as ribonuclease and deoxyribonuclease activities. RIPs have been shown to manifest abortifacient, anti-tumor, anti-viral and anti-microbial activities. RIPs are detected in some medicinal plants but the yields are insufficient to warrant their availability to conduct clinical trials for therapeutic application. Here, we describe an approach based on “bioprocess development” that may enhance the yield of RIPs and eventually their availability for exploiting their therapeutic potential.

Ribosome inactivating proteins (RIPs) from momordica charantia for anti viral therapy

This review describes the nature and applications of ribosome inactivating proteins (RIPs) from Momordica charantia (bitter melon). RIPs from the plant kingdom have received much attention in biomedical research because they target conserved host protein synthesis machinery and show specificity towards human and animal cell targets. Recent studies aimed at unravelling the enzymatic activities of the M charantia RIPs provide a structural basis for their activities. It has been reported that RIPs are member of the single chain ribosome inactivating protein (SCRIP) family which act irreversibly on ribosome by removing adenine residue from eukaryotic ribosomal RNA. Various activities of RIPs include anti-tumor, broad anti-viral, ribonuclease and deoxyribonuclease. MAP30 (Momordica Anti-HIV Protein), alpha- and beta-momorcharins inhibit HIV replication in acutely and chronically infected cells and thus are considered potential therapeutic agent in HIV infection and AIDS. Further, MAP30 improved the efficacy of anti-HIV therapy when used in combination with other anti-viral drugs. MAP30 holds therapeutic promise over other RIPs because not only it is active against infection and replication of both HSV and HIV but is non toxic to normal cells. Here we review the nature, action, structure function relationship and applications of RIPs from Momordica charantia and evaluate their potential for anti-cancer and anti-viral therapy.

Heterotrimeric G proteins-mediated resistance to necrotrophic pathogens includes mechanisms independent of salicylic acid-, jasmonic acid/ethylene- and abscisic acid-mediated defense signaling

Heterotrimeric G proteins are involved in the defense response against necrotrophic fungi in Arabidopsis. In order to elucidate the resistance mechanisms involving heterotrimeric G proteins, we analyzed the effects of the Gβ (subunit deficiency in the mutant agb1-2 on pathogenesis-related gene expression, as well as the genetic interaction between agb1-2 and a number of mutants of established defense pathways. Gβ-mediated signaling suppresses the induction of salicylic acid (SA)-, jasmonic acid (JA)-, ethylene (ET)- and abscisic acid (ABA)-dependent genes during the initial phase of the infection with Fusarium oxysporum (up to 48 h after inoculation). However, at a later phase it enhances JA/ET-dependent genes such as PDF1.2 and PR4. Quantification of the Fusarium wilt symptoms revealed that Gβ- and SA-deficient mutants were more susceptible than wild-type plants, whereas JA- and ET-insensitive and ABA-deficient mutants demonstrated various levels of resistance. Analysis of the double mutants showed that the Gβ-mediated resistance to F. oxysporum and Alternaria brassicicola was mostly independent of all of the previously mentioned pathways. However, the progressive decay of agb1-2 mutants was compensated by coi1-21 and jin1-9 mutations, suggesting that at this stage of F. oxysporum infection Gβ acts upstream of COI1 and ATMYC2 in JA signaling.

Heterotrimeric G proteins facilitate arabidopsis resistance to necrotrophic pathogens and are involved in jasmonate signaling

Heterotrimeric G proteinshave been previously linked to plant defense; however a role for the Gbg dimer in defense signaling has not been described to date. Using available Arabidopsis (Arabidopsis thaliana) mutants lacking functional Ga or Gb subunits, we show that defense against the necrotrophic pathogens Alternaria brassicicola and Fusarium oxysporum is impaired in Gb-deficient mutants while Ga-deficient mutants show slightly increased resistance compared to wild-type Columbia ecotype plants. In contrast, responses to virulent (DC3000) and avirulent (JL1065) strains of Pseudomonas syringae appear to be independent of heterotrimeric G proteins. The induction of a number of defense-related genes in Gb-deficient mutants were severely reduced in response to A. brassicicola infection. In addition, Gb-deficient mutants exhibit decreased sensitivity to a number of methyl jasmonate-induced responses such as induction of the plant defensin gene PDF1.2, inhibition of root elongation, seed germination, and growth of plants in sublethal concentrations of methyl jasmonate. In all cases, the behavior of the Ga-deficient mutants is coherent with the classic heterotrimeric mechanism of action, indicating that jasmonic acid signaling is influenced by the Gbg functional subunit but not by Ga. We hypothesize that Gbg acts as a direct or indirect enhancer of the jasmonate signaling pathway in plants.

Abscisic acid regulation of plant defence responses during pathogen attack

The plant hormone, abscisic acid (ABA), has previously been shown to have an impact on the resistance or susceptibility of plants to pathogens. In this thesis, it was shown that ABA had a regulatory effect on an extensive array of plant defence responses in three different plant and pathogen interaction combinations as well as following the application of an abiotic elicitor. In unique studies using ABA deficient mutants of Arabidopsis, exogenous ABA addition or ABA biosynthesis inhibitor application and simulated drought stress, ABA was shown to have a profound effect on the outcome of interactions between plants and pathogens of differing lifestyles and from different kingdoms. The systems used included a model plant and an important agricultural species: Arabidopsis thaliana (Arabidopsis) and Peronospora parasitica (a biotrophic Oomycete pathogen), Arabidopsis and Pseudomonas syringae pathovar tomato (a biotrophic bacterial pathogen) and an unrelated plant species, soybean (Glycine max) and Phytophthora sojae (a hemibiotrophic Oomycete pathogen), Generally, a higher than basal endogenous ABA concentration within plant tissues at the time of avirulent pathogen inoculation, caused an interaction shift towards what phenotypically resembled susceptibility. Conversely, a lower than basal endogenous ABA concentration in plants inoculated with a virulent pathogen caused a shift towards resistance. An extensive suppressive effect of ABA on defence responses was revealed by a range of techniques that included histochemical, biochemical and molecular approaches. A universal effect of ABA on suppression or induction of the phenylpropanoid pathway via regulation of the key entry point gene, phenylalanine ammonia-lyase (PAL), when stimulated by biotic or abiotic elicitors was shown. ABA also influenced a wide variety of other defence-related components such as: the development of a hypersensitive response (HR), the accumulation of the reactive oxyden species, hydrogen peroxide and the cell wall strengthening compounds lignin and callose, accumulation of SA and the phytoalexin, glyceollin and the transcription of the SA-dependent pathogenesis- related gene (PR-1). The near genome-wide microarray gene expression analysis of an ABA induced susceptible interaction also revealed an yet unprecedented insight into the great diversity of defence responses that were influenced by ABA that included: disease resistance like proteins, antimicrobial proteins as well as phenylpropanoid and tryptophan pathway enzymes. Subtle differences were found in the number and type of defence responses that were regulated by ABA in each type of plant and pathogen interaction that was studied. This thesis has clearly identified in plant/pathogen interactions previously unknown and important roles for ABA in the regulation of many defence responses.

Characterisation and physiological functions of plant natriuretic peptides

Natriuretic peptides are bioactive proteins. In plants, biochemical and physiological studies on these molecules has now revealed that they influence stomatal opening, cell volume and the activity of membrane pumps and their localisation within vascular tissues. Thus they have major roles in maintaining water and solute homeostasis.

Characterization of Type 1 ribosome inactivating proteins in edible plants

The ribosome inactivating proteins (RIPs) from plants possess RNA N-glycosidase activity that depurinates the major rRNA, thus damaging ribosome in an irreversible manner and arresting protein synthesis. RIPs occur in fungi, bacteria and plants and are abundant in angiosperms, where they appear to have defensive role. RIPs are presently classified as rRNA N-glycosidase in the enzyme nomenclature (EC 3.2.2.22) and do exhibit other enzymatic activities such as ribonuclease and deoxyribonuclease activities. RIPs are classified into two groups based on their difference in their primary structure. Type I RIPs consist of a single polypeptide chain of approximately 26–35 kDa that possess an RNA N-glycosidase activity. These proteins have attracted a great deal of attention because of their anti-viral, anti-tumor, and anti-microbial activities, which is useful in medical research and development. Here, we describe isolation of a novel protein from Momordica sp, a highclimbing vine from family Cucurbitaceae which is native to the tropical regions of Africa, Asia, Arabia and Caribbean. The purified protein has been verified by SDS-PAGE and mass spectrometry to contain only single chain Type-1 ribosome inactivating proteins (RIPs). With present experiments, we determined the presence of RIPs in edible plant materials, including some that are eaten raw by human beings. The novel protein is further characterized to validate its therapeutic potential.