Abstract
Brassinosteroids (BRs) are plant specific steroidal hormones that play diverse roles in regulating a broad spectrum of plant growth and developmental processes, as well as, in responding to various biotic and abiotic stresses. Extensive research over the years has established stress-impact-mitigating role of BRs and associated compounds in different plants exposed to various abiotic and biotic stresses, suggesting the idea that they may act as immunomodulators, thus opening new approaches for plant resistance against hazardous environmental conditions. In this research the characterization of the transcriptional response of 11 transcription factors (TFs) belonging to BRASSINAZOLE-RESISTANT 1 (BZR1) TF family of Zea mays L. was analyzed in seedlings subjected to different stress conditions. Being important regulators of the BR synthesis, BZR TFs might have stress resistance related activities. However, no stress resistance related functional study of BZR TFs has been reported in maize so far. In silico analyses of the selected 11 TFs validated the features of their protein domains, where the highest degree of similarity observed with recognized BZR TFs of rice and Sorghum bicolor. Additionally, we investigated the organ-specific expression of 11 ZmBZR in maize seedlings. Five of them did not show any transcript accumulation, suggesting that ZmBZR expression might be regulated in a manner dependent on plant developmental stage. For the remaining six ZmBZR, their ubiquitous expression in the whole plant indicates they could function as growth regulators during maize development. More importantly, in response to various stress conditions, the spatial transcript accumulation of all ZmBZR varies along the plant. All six ZmBZR showed up-regulation against N starvation, hypoxia and salt stress. On the contrary, heat stress clearly down-regulated gene expression of all ZmBZR analysed. Consistently with the expression results, the distribution of stress-related cis-acting elements in the promoter of these genes inferred that the maize BZR TFs might play some roles in regulating the expression of the corresponding genes in response to multifarious stresses. In conclusion, these data reveal that BZR TFs have stress signaling activity in maize, in addition to their confirmed role in regulating plant physiology and morphology.
Highlights
Brassinosteroids (BRs) are plant specific steroidal hormones that play diverse roles in regulating a broad spectrum of plant growth and developmental processes
To identify BZR transcription factors (TFs) family members in Zea mays L., the Arabidopsis BRASSINAZOLE-RESISTANT 1 (BZR1) amino acid sequence was used as query to search the maize Database (Phytozome)
In order to identify BZR genes in Zea mays L. genome (B 73 RefGen_V3), the Arabidopsis BZR protein sequences were used as query to perform a genome-wide search
Summary
Brassinosteroids (BRs) are plant specific steroidal hormones that play diverse roles in regulating a broad spectrum of plant growth and developmental processes. They regulate multiple physiological functions including seed germination, cell elongation and division, senescence, vascular-differentiation, reproduction, root development, photomorphogenesis and respond to various biotic and abiotic stresses (Saini et al 2015; Singh and SavaldiGoldstein 2015). Extensive research over the years has led to the idea that BRs could act as stressimpact-mitigating compounds in different plants exposed to various abiotic stresses such as high temperature, low temperature in terms of chilling and freezing, salinity, light, drought, metals/metalloids and organic pollutants (Derevyanchuk et al 2016; Vardhini and Anjum 2015 and references therein). BRs seem to act as immunomodulators when applied at the appropriate concentration and at the correct stage of plant development, opening new approaches for the improvement of plant resistance against hazardous environmental conditions
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