RESUMO
Low temperatures, salinity, and drought cause significant crop losses. These conditions involve osmotic stress, triggering transcriptional remodeling, and consequently, the restitution of cellular homeostasis and growth recovery. Protein transcription factors regulate target genes, thereby mediating plant responses to stress. bZIP17 is a transcription factor involved in cellular responses to salinity and the unfolded protein response. Because salinity can also produce osmotic stress, the role of bZIP17 in response to osmotic stress was assessed. Mannitol treatments induced the transcript accumulation and protein processing of bZIP17. Transcriptomic analyses showed that several genes associated with seed storage and germination showed lower expression in bzip17 mutants than in wild-type plants. Interestingly, bZIP17 transcript was more abundant in seeds, and germination analyses revealed that wild-type plants germinated later than bzip17 mutants in the presence of mannitol, but no effects were observed when the seeds were exposed to ABA. Finally, the transcript levels of bZIP17 target genes that control seed storage and germination were assessed in seeds exposed to mannitol treatments, which showed lower expression levels in bzip17 mutants compared to the wild-type seeds. These results suggest that bZIP17 plays a role in osmotic stress, acting as a negative regulator of germination through the regulation of genes involved in seed storage and germination.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Regulação da Expressão Gênica de Plantas/fisiologia , Germinação/fisiologia , Pressão Osmótica/fisiologia , Sementes/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Fatores de Transcrição de Zíper de Leucina Básica/genética , Sementes/genéticaRESUMO
Plants can be severely affected by salt stress. Since these are sessile organisms, they have developed different cellular responses to cope with this problem. Recently, it has been described that bZIP17 and bZIP60, two ER-located transcription factors, are involved in the cellular response to salt stress. On the other hand, bZIP60 is also involved in the unfolded protein response (UPR), a signaling pathway that up-regulates the expression of ER-chaperones. Coincidentally, salt stress produces the up-regulation of BiP, one of the main chaperones located in this organelle. Then, it has been proposed that UPR is associated to salt stress. Here, by using insertional mutant plants on bZIP17 and bZIP60, we show that bZIP17 regulate the accumulation of the transcript for the chaperone BiP3 under salt stress conditions, but does not lead to the accumulation of UPR-responding genes such as the chaperones Calnexin, Calreticulin, and PDIL under salt treatments. In contrast, DTT, a known inducer of UPR, leads to the up-regulation of all these chaperones. On the other hand, we found that bZIP60 regulates the expression of some bZIP17 target genes under conditions were splicing of bZIP60 does not occur, suggesting that the spliced and unspliced forms of bZIP60 play different roles in the physiological response of the plant. Our results indicate that the ER-located transcription factors bZIP17 and bZIP60 play a role in salt stress but this response goes through a signaling pathway that is different to that triggered by the unfolded protein response.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Fatores de Transcrição de Zíper de Leucina Básica/genética , Chaperonas Moleculares/genética , Processamento Alternativo , Arabidopsis/metabolismo , Ditiotreitol/farmacologia , Regulação da Expressão Gênica de Plantas , Salinidade , Estresse Fisiológico , Resposta a Proteínas não Dobradas/efeitos dos fármacosRESUMO
Cherimoyas (Annona cherimola), like other subtropical/tropical fruits, are susceptible to damage from exposure to temperatures between 0 and 5 °C (chilling injury, CI), which may affect fruit quality. To increase our understanding of the molecular mechanisms involved in the CI response, a forward suppression subtractive hybridization (SSH) cDNA library was constructed. In this work, we obtained 75 genes that could potentially be involved in the CI response. The CI induced activation of genes that are involved in a range of metabolic pathways, such as primary metabolism, transport, and endomembrane traffic, among others. We also characterized the expression of 12 selected genes in different A. cherimola tissues by polymerase chain reaction (PCR), and we confirmed the differential expression of a subset in CI fruits by real-time quantitative PCR (qPCR). The expression of six A. cherimola genes: annexin (AcAnex), UDP-glucose pyrophosphorylase (AcUGP), syntaxin of plants 71 (AcSyp71), 1-aminocyclopropane-1-carboxylic-acid synthase (AcACS), ubiquitin carrier-like protein (AcUCP), and enolase (AcEnol), was up-regulated after cold storage for 12 days at 0 °C. These results imply that selected genes could be related to the development of internal browning observed in cherimoyas after exposure to CI conditions. The information generated in this study provides new clues that may aid in understanding the cherimoya ripening process.