Aux/IAA proteins are well-known as key components of the nuclear auxin signaling pathway, repressing gene transcription when present and enabling gene activation upon their degradation. In this review, we explore the additional roles of Aux/IAA proteins in the known auxin perception pathways-the TIR1/AFBs nuclear as well as in the emerging cytoplasmic and apoplastic pathways. We summarize recent advances in understanding the regulation of Aux/IAA protein stability at the post-translational level, a critical factor in auxin-regulated transcriptional output. We further highlight the roles of auxin-nondegradable non-canonical Aux/IAAs in auxin-mediated transcription and their involvement in apoplastic auxin signalling. Additionally, we discuss the importance of Aux/IAAs for the adenylate cyclase activity of TIR1/AFB receptors and speculate on their involvement in the cytoplasmic auxin pathway. Using Arabidopsis root as a model, this work underscores the central role of Aux/IAA proteins in mediating auxin-driven developmental processes and environmental responses. Key questions for future research are proposed to further unravel the dynamic roles of Aux/IAAs in auxin signaling networks.

• MeSH
• Arabidopsis * metabolismus   genetika   MeSH
• F-box proteiny metabolismus   genetika   MeSH
• kořeny rostlin metabolismus   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• receptory buněčného povrchu metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin * metabolismus   MeSH
• rostlinné proteiny * metabolismus   genetika   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• F-box proteiny MeSH
• kyseliny indoloctové * MeSH
• proteiny huseníčku * MeSH
• receptory buněčného povrchu MeSH
• regulátory růstu rostlin * MeSH
• rostlinné proteiny * MeSH

The plant-signaling molecule auxin triggers fast and slow cellular responses across land plants and algae. The nuclear auxin pathway mediates gene expression and controls growth and development in land plants, but this pathway is absent from algal sister groups. Several components of rapid responses have been identified in Arabidopsis, but it is unknown if these are part of a conserved mechanism. We recently identified a fast, proteome-wide phosphorylation response to auxin. Here, we show that this response occurs across 5 land plant and algal species and converges on a core group of shared targets. We found conserved rapid physiological responses to auxin in the same species and identified rapidly accelerated fibrosarcoma (RAF)-like protein kinases as central mediators of auxin-triggered phosphorylation across species. Genetic analysis connects this kinase to both auxin-triggered protein phosphorylation and rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.

• Klíčová slova
• RAF kinase, auxin, plant evolution, protein phosphorylation,
• MeSH
• Arabidopsis genetika   metabolismus   MeSH
• bílkoviny řas metabolismus   MeSH
• fosforylace MeSH
• kyseliny indoloctové metabolismus   MeSH
• proteinkinasy metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné proteiny metabolismus   MeSH
• rostliny metabolismus   MeSH
• signální transdukce * MeSH
• vyšší rostliny * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bílkoviny řas MeSH
• kyseliny indoloctové MeSH
• proteinkinasy MeSH
• rostlinné proteiny MeSH

Expansins facilitate cell expansion by mediating pH-dependent cell wall (CW) loosening. However, the role of expansins in controlling CW biomechanical properties in specific tissues and organs remains elusive. We monitored hormonal responsiveness and spatial specificity of expression and localization of expansins predicted to be the direct targets of cytokinin signaling in Arabidopsis (Arabidopsis thaliana). We found EXPANSIN1 (EXPA1) homogenously distributed throughout the CW of columella/lateral root cap, while EXPA10 and EXPA14 localized predominantly at 3-cell boundaries in the epidermis/cortex in various root zones. EXPA15 revealed cell-type-specific combination of homogenous vs. 3-cell boundaries localization. By comparing Brillouin frequency shift and AFM-measured Young's modulus, we demonstrated Brillouin light scattering (BLS) as a tool suitable for non-invasive in vivo quantitative assessment of CW viscoelasticity. Using both BLS and AFM, we showed that EXPA1 overexpression upregulated CW stiffness in the root transition zone (TZ). The dexamethasone-controlled EXPA1 overexpression induced fast changes in the transcription of numerous CW-associated genes, including several EXPAs and XYLOGLUCAN:XYLOGLUCOSYL TRANSFERASEs (XTHs), and associated with rapid pectin methylesterification determined by in situ Fourier-transform infrared spectroscopy in the root TZ. The EXPA1-induced CW remodeling is associated with the shortening of the root apical meristem, leading to root growth arrest. Based on our results, we propose that expansins control root growth by a delicate orchestration of CW biomechanical properties, possibly regulating both CW loosening and CW remodeling.

• MeSH
• Arabidopsis * metabolismus   MeSH
• biomechanika MeSH
• buněčná stěna metabolismus   MeSH
• hormony metabolismus   MeSH
• kořeny rostlin metabolismus   MeSH
• meristém metabolismus   MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• EXPA1 protein, Arabidopsis MeSH Prohlížeč
• hormony MeSH
• proteiny huseníčku * MeSH