RESUMO
Medicago truncatula is a model legume forage crop native to the arid and semi-arid environments of the Mediterranean. Given its drought-adapted nature, it is an ideal candidate to study the molecular and biochemical mechanisms conferring drought resistance in plants. Medicago plants were subjected to a progressive drought stress over 14 d of water withholding followed by rewatering under controlled environmental conditions. Based on physiological measurements of plant water status and changes in morphology, plants experienced mild, moderate and severe water stress before rehydration. Transcriptome analysis of roots and shoots from control, mildly, moderately and severely stressed, and rewatered plants, identified many thousands of genes that were altered in expression in response to drought. Many genes with expression tightly coupled to the plant water potential (i.e. drought intensity) were identified suggesting an involvement in Medicago drought adaptation responses. Metabolite profiling of drought-stressed plants revealed the presence of 135 polar and 165 non-polar compounds in roots and shoots. Combining Medicago metabolomic data with transcriptomic data yielded insight into the regulation of metabolic pathways operating under drought stress. Among the metabolites detected in drought-stressed Medicago plants, myo-inositol and proline had striking regulatory profiles indicating involvement in Medicago drought tolerance.
Assuntos
Secas , Medicago truncatula/genética , Medicago truncatula/metabolismo , Transcrição Gênica , Água/metabolismo , Análise por Conglomerados , Regulação da Expressão Gênica de Plantas , Ontologia Genética , Genes de Plantas , Medicago truncatula/efeitos dos fármacos , Medicago truncatula/fisiologia , Metaboloma/genética , Folhas de Planta/metabolismo , Raízes de Plantas/genética , Brotos de Planta/genética , Software , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genética , Fatores de Tempo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica/efeitos dos fármacos , Transcriptoma/genética , Água/farmacologiaRESUMO
A full-length cDNA encoding a putative aspartic acid protease (AcAP1) was isolated for the first time from the flesh of pineapple (Ananas comosus) fruit. The deduced sequence of AcAP1 showed all the common features of a typical plant aspartic protease phytepsin precursor. Analysis of AcAP1 gene expression under postharvest chilling treatment in two pineapple varieties differing in their resistance to blackheart development revealed opposite trends. The resistant variety showed an up-regulation of AcAP1 precursor gene expression whereas the susceptible showed a down-regulation in response to postharvest chilling treatment. The same trend was observed regarding specific AP enzyme activity in both varieties. Taken together our results support the involvement of AcAP1 in postharvest chilling stress resistance in pineapple fruits.
Assuntos
Ananas/genética , Ácido Aspártico Proteases/genética , Proteínas de Plantas/genética , Ananas/metabolismo , Ácido Aspártico Proteases/química , Clonagem Molecular , Temperatura Baixa , DNA Complementar/química , Filogenia , Proteínas de Plantas/química , Análise de Sequência de Proteína , Estresse Fisiológico/genéticaRESUMO
Blackheart is a physiological disorder induced by postharvest chilling storage during pineapple fruit export shipping. The aim of this study was to check the involvement of bromelain, the cysteine protease protein family abundantly present in pineapple fruits, and AcCYS1, an endogenous inhibitor of bromelain, in the development of blackheart. For this we checked the response to postharvest chilling treatment of two pineapple varieties (MD2 and Smooth Cayenne) differing in their resistance to blackheart. Quantitative RT-PCR analyses showed that postharvest chilling treatment induced a down-regulation of bromelain transcript accumulation in both varieties with the most dramatic drop in the resistant variety. Regarding AcCYS1 transcript accumulation, the varieties showed opposite trends with an up-regulation in the case of the resistant variety and a down-regulation in the susceptible one. Taken together our results suggest that the control of bromelain and AcCYS1 expression levels directly correlates to the resistance to blackheart development in pineapple fruits.
Assuntos
Ananas/fisiologia , Bromelaínas/genética , Cistatinas/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Ananas/genética , Bromelaínas/metabolismo , Temperatura Baixa , Cistatinas/metabolismo , Frutas/genética , Frutas/fisiologia , Dados de Sequência Molecular , Proteínas de Plantas/metabolismo , Reação em Cadeia da Polimerase , Análise de Sequência de DNARESUMO
Glutathione (GSH) is an abundant metabolite and a major antioxidant in plant cells. However, in the Leguminosae, homoglutathione (hGSH) may replace glutathione (GSH) partially or completely. To date, cowpea (Vigna unguiculata) has been considered a non-hGSH-producing species, and no hGSHS cDNA has been isolated. Here we report on the cloning of a full-length cDNA coding for a hGSHS (EC 6.3.2.23) and the cloning of a partial cDNA coding for a putative glutathione synthetase (GSHS; EC 6.3.2.3) in cowpea leaf extracts. These cDNAs possess, respectively, the leucine/proline hGSHS signature and the alanine/alanine GSHS signature at the 3' end. Expression analysis showed a significant up-regulation of hGSHS during progressive drought stress that could be directly related to the drought tolerance of the cowpea cultivar used, while GSHS was mainly constitutively expressed. Nevertheless, quantification of low-molecular-weight thiols confirmed the previous findings that cowpea is essentially a GSH producing plant, as no hGSH was detected in the leaves. These findings raise new questions regarding the function, activity and substrate specificity of the cloned hGSHS cDNA. These questions are discussed.
Assuntos
Secas , Fabaceae/enzimologia , Fabaceae/metabolismo , Glutationa Sintase/genética , Peptídeo Sintases/genética , Folhas de Planta/metabolismo , Compostos de Sulfidrila/química , Compostos de Sulfidrila/metabolismo , Sequência de Aminoácidos , Cromatografia Líquida de Alta Pressão , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Glutationa Sintase/química , Glutationa Sintase/metabolismo , Dados de Sequência Molecular , Peso Molecular , Peptídeo Sintases/química , Peptídeo Sintases/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de AminoácidosRESUMO
Dehydrins (DHNs) are proteins that accumulate abundantly in various plant tissues in response to environmental stresses and during seed maturation, possibly assisting cells in tolerating dehydration. White lupins (Lupinus albus L.) are able to withstand periods of severe water deficit (WD) and previous work suggested that the stem plays a central role as a survival structure. To investigate DHNs involvement in this strategy, we studied tissue specific protein accumulation of a RAB16-like DHN in lupin during a progressive WD and early recovery. Differences were found between leaves, stems and roots. In leaves and roots, the accumulation of the RAB16-like DHN was independent of the water status whereas in the stem (cortex and stele), DHNs were only detected under severe plant WD (stele relative water content, RWC, reduction of 6-7% and cortex RWC reduction of 20%). DHN mRNA analysis by RT-PCR, showed the presence of one DHN mRNA regardless of the tissue or the plant water status.
RESUMO
A cowpea (Vigna unguiculata cv. EPACE-1) aspartic proteinase (AP) gene was isolated by genomic Library screening. Sequence analysis shows that this AP gene follows the same pattern of intron/exon number and organization as the other isolated plant AP genes, which are distinct from other solved AP genes. Northern blot analysis revealed that cowpea AP accumulates in leaves and stems but not in roots, indicating tissue-specific expression. An increased accumulation of transcripts during senescence suggests enzyme involvement in this process.
