Differential expression of bean chitinase genes by virus infection, chemical treatment and UV irradiation

Abstract

Three chitinases have been shown previously to be induced upon various stresses of bean leaves. Time course studies of mRNA accumulation of two of them (P3- and P4-chitinases) have been studied upon virus infection, mercuric chloride treatment and UV irradiation. In alfalfa mosaic virus (AlMV)-infected plants both mRNAs, absent in uninfected bean leaves, become detectable 36 h after inoculation. A maximum level of mRNAs is reached 84 h after inoculation and, whereas the amount of P3-ch mRNA decreases soon after having reached the maximum, the amount of P4-ch mRNA remains at high levels for several days. In mercuric chloride-treated leaves P4-ch mRNA becomes detectable 1-1.5 h after onset of treatment and a maximum level is observed between 6 h and 24 h after treatment; P3-ch mRNA becomes detectable later than P4-ch mRNA in treated leaves and reaches a maximum as late as 18 h after treatment has been applied. UV light also induces the synthesis of both mRNAs but, here again, important differences are observed in the accumulation rate of the two transcripts. The relative amounts of each mRNA induced by the different stresses have been compared. The most effective inducer of P3-ch mRNA is AlMV. In contrast, mercuric chloride induces P4-ch mRNA more efficiently than AlMV or UV light. We have also determined the complete nucleotide sequence of the cDNA encoding P3-chitinase that has been isolated from a cDNA library by using the cucumber lysozyme-chitinase cDNA as a probe. The 1072 bp P3-ch cDNA encodes a mature protein of 268 amino acid residues and the 25 residue NH2-terminal signal peptide of the precursor. Because of its high structural homology to the cucumber and Arabidopsis acidic chitinases as well as to the N-terminal amino acid sequence of the bifunctional lysozyme-chitinase from P. quinquifolia, bean P3-chitinase can be considered to belong to the class III chitinases. Southern blot analysis of bean genomic DNA revealed that P3-chitinase is encoded by a single gene.

Antifreeze Proteins in Winter Rye Are Similar to Pathogenesis-Related Proteins

“…Instead, these results imply that the AFPs may be nove1 proteins with similarity to PR proteins. PR proteins are known to be encoded by small gene families (Stintzi et al, 1993), and isoforms within each family are differentially expressed in response to various environmental stimuli (Margis-Pinheiro et al, 1993).…”

Plant defence genes are induced in the pathogenic interaction between bean roots and Fusarium solani, but not in the symbiotic interaction with the arbuscular mycorrhizal fungus Glomus mosseae

“…The cDNA clone pCH18, encoding class I chitinase (Broglie, Gaynor & Broglie, 1986) was from Dr R. Broglie (DuPont, Wilmington, DE, USA), cDNA clones encoding class III (Margis-Pinheiro et al, 1993) and class IV chitinase (Margis-Pinheiro et al, 1991) were obtained from Dr G. Burkard (Institut de Biologie Mole! culaire des Plantes du CNRS, Strasbourg, France).…”

Danos causados por pragas na estrutura, morfologia e composição de híbridos de milho Bt para silagem

“…Os mecanismos de defesa são ativados pela atuação de um agente agressor, sendo os indutores de resposta endógenos (fragmentos da própria planta, substâncias derivadas de componentes estruturais da planta liberadas pelo ataque de enzimas) ou exógenos (fragmentos do agente agressor) (MARGIS-PINHEIRO et al, 1993). Embora as pragas tenham que ingerir tecidos da planta para que a proteína Cry1Ab possa intoxicá-las, talvez a intensidade deste ataque não seja suficiente para desencadear mecanismos de defesa da planta.…”

“…As proteínas HRGP acumulam-se alterando a estrutura das paredes celulares para criar uma barreira estrutural, de forma direta ou preparando locais para o depósito de lignina (MARGIS-PINHEIRO et al, 1993).…”