title: Salt-induced delay in cotyledonary globulin mobilization is abolished by induction of proteases and leaf growth sink strength at late seedling establishment in cashew.
abstract: Seedling establishment in saline conditions is crucial for plant survival and productivity. This study was performed to elucidate the biochemical and physiological mechanisms involved with the recovery and establishment of cashew seedlings subjected to salinity. The changes in the Na+ levels and K/Na ratios, associated with relative water content, indicated that osmotic effects were more important than salt toxicity in the inhibition of seedling growth and cotyledonary protein mobilization. Salinity (50mM NaCl) induced a strong delay in protein breakdown and amino acid accumulation in cotyledons, and this effect was closely related to azocaseinolytic and protease activities. In parallel, proline and free amino acids accumulated in the leaves whereas the protein content decreased. Assays with specific inhibitors indicated that the most important proteases in cotyledons were of serine, cysteine and aspartic types. Proteomic analysis revealed that most of the cashew reserve proteins are 11S globulin-type and that these proteins were similarly degraded under salinity. In the late establishment phase, the salt-treated seedlings displayed an unexpected recovery in terms of leaf growth and N mobilization from cotyledon to leaves. This recovery coordinately involved a great leaf expansion, decreased amino acid content and increased protein synthesis in leaves. This response occurred in parallel with a prominent induction in the cotyledon proteolytic activity. Altogether, these data suggest that a source-sink mechanism involving leaf growth and protein synthesis may have acted as an important sink for reserve mobilization contributing to the seedling establishment under salinity. The amino acids that accumulated in the leaves may have exerted negative feedback to act as a signal for the induction of protease activity in the cotyledon. Overall, these mechanisms employed by cashew seedlings may be part of an adaptive process for the efficient rescue of cotyledonary proteins, as the cashew species originates from an environment with N-poor soil and high salinity.
authors.affiliation: Centro de Ciências Agrárias e Biológicas, Universidade Estadual Vale do Acaraú, CEP 62040-370, Sobral, CE, Brazil.
authors.forename: Luiz Ferreira Aguiar
authors.initials: LF
authors.lastname: Ponte
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, CEP 60451-970, Fortaleza, Ceará, Brazil.
authors.forename: André Luis Coelho da
authors.initials: AL
authors.lastname: Silva
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, CEP 60451-970, Fortaleza, Ceará, Brazil.
authors.forename: Fabrício Eulálio Leite
authors.initials: FE
authors.lastname: Carvalho
authors.affiliation: Campos IV - Catolé do Rocha, Centro de Ciências Humanas e Agrárias, CCHA, Universidade Estadual da Paraiba, Paraiba, Brazil.
authors.forename: Josemir Moura
authors.initials: JM
authors.lastname: Maia
authors.affiliation: Laboratório de Estudos em Biotecnologia Vegetal, Departamento de Biologia Celular e Genética, Universidade Federal do Rio Grande do Norte, RN, Brazil.
authors.forename: Eduardo Luiz
authors.initials: EL
authors.lastname: Voigt
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, CEP 60451-970, Fortaleza, Ceará, Brazil. Electronic address: silveira@ufc.br.
authors.forename: Joaquim Albenisio Gomes
authors.initials: JA
authors.lastname: Silveira
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D031021:Anacardium / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D001692:Biological Transport; D018548:Cotyledon / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D005916:Globulins / Q000378:metabolism*; D009997:Osmotic Pressure; D010447:Peptide Hydrolases / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D040901:Proteomics; D054712:Salinity; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D000596:Amino Acids; D005916:Globulins; D010940:Plant Proteins; D012965:Sodium Chloride; D011392:Proline; D010447:Peptide Hydrolases
keywords: Anacardium occidentale; Plant establishment; Proteases; Protein metabolism; Salinity