RESUMO
Reactive oxygen species (ROS) are essential signaling molecules that enable cells to respond rapidly to a range of stimuli. The ability of plants to recognize various stressors, incorporate a variety of environmental inputs, and initiate stress-response networks depends on ROS. Plants develop resilience and defensive systems as a result of these processes. Root hairs are central components of root biology since they increase the surface area of the root, anchor it in the soil, increase its ability to absorb water and nutrients, and foster interactions between microorganisms. In this review, we specifically focused on root hair cells and we highlighted the identification of ROS receptors, important new regulatory hubs that connect ROS production, transport, and signaling in the context of two hormonal pathways (auxin and ethylene) and under low temperature environmental input related to nutrients. As ROS play a crucial role in regulating cell elongation rates, root hairs are rapidly gaining traction as a very valuable single plant cell model for investigating ROS homeostasis and signaling. These promising findings might soon facilitate the development of plants and roots that are more resilient to environmental stressors.
Assuntos
Raízes de Plantas , Espécies Reativas de Oxigênio , Espécies Reativas de Oxigênio/metabolismo , Raízes de Plantas/metabolismo , Raízes de Plantas/fisiologia , Transdução de SinaisRESUMO
Major constituents of the plant cell walls are structural proteins that belong to the hydroxyproline-rich glycoprotein (HRGP) family. Leucine-rich repeat extensin (LRX) proteins contain a leucine-rich domain and a C-terminal domain with repetitive Ser-Pro3-5 motifs that are potentially to be O-glycosylated. It has been demonstrated that pollen-specific LRX8-LRX11 from Arabidopsis thaliana are necessary to maintain the integrity of the pollen tube cell wall during polarized growth. In HRGPs, including classical extensins (EXTs), and probably in LRXs, proline residues are converted to hydroxyproline by prolyl-4-hydroxylases (P4Hs), thus defining novel O-glycosylation sites. In this context, we aimed to determine whether hydroxylation and subsequent O-glycosylation of Arabidopsis pollen LRXs are necessary for their proper function and cell wall localization in pollen tubes. We hypothesized that pollen-expressed P4H4 and P4H6 catalyze the hydroxylation of the proline units present in Ser-Pro3-5 motifs of LRX8-LRX11. Here, we show that the p4h4-1 p4h6-1 double mutant exhibits a reduction in pollen germination rates and a slight reduction in pollen tube length. Pollen germination is also inhibited by P4H inhibitors, suggesting that prolyl hydroxylation is required for pollen tube development. Plants expressing pLRX11::LRX11-GFP in the p4h4-1 p4h6-1 background show partial re-localization of LRX11-green fluorescent protein (GFP) from the pollen tube tip apoplast to the cytoplasm. Finally, immunoprecipitation-tandem mass spectrometry analysis revealed a decrease in oxidized prolines (hydroxyprolines) in LRX11-GFP in the p4h4-1 p4h6-1 background compared with lrx11 plants expressing pLRX11::LRX11-GFP. Taken together, these results suggest that P4H4 and P4H6 are required for pollen germination and for proper hydroxylation of LRX11 necessary for its localization in the cell wall of pollen tubes.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Tubo Polínico , Prolil Hidroxilases , Arabidopsis/metabolismo , Arabidopsis/genética , Hidroxilação , Tubo Polínico/crescimento & desenvolvimento , Tubo Polínico/metabolismo , Tubo Polínico/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Prolil Hidroxilases/metabolismo , Prolil Hidroxilases/genética , Parede Celular/metabolismoRESUMO
Population expansion is a global issue, especially for food production. Meanwhile, global climate change is damaging our soils, making it difficult for crops to thrive and lowering both production and quality. Poor nutrition and salinity stress affect plant growth and development. Although the impact of individual plant stresses has been studied for decades, the real stress scenario is more complex due to the exposure to multiple stresses at the same time. Here we investigate using existing evidence and a meta-analysis approach to determine molecular linkages between two contemporaneous abiotic stimuli, phosphate (Pi) deficiency and salinity, on a single plant cell model, the root hairs (RHs), which is the first plant cell exposed to them. Understanding how these two stresses work molecularly in RHs may help us build super-adaptable crops and sustainable agriculture in the face of global climate change.
RESUMO
Eukaryotic cells' proliferation and growth are controlled by the target of rapamycin kinase (TOR). TOR usually activates in favorable energy and nutritional circumstances. This is challenged by recent research, suggesting that plant cells optimized for nutrient absorption in low nutritional conditions may activate the TOR pathway in a polarized manner.
Assuntos
Nutrientes , Sirolimo , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismoRESUMO
Plant genomes encode a unique group of papain-type Cysteine EndoPeptidases (CysEPs) containing a KDEL endoplasmic reticulum (ER) retention signal (KDEL-CysEPs or CEPs). CEPs process the cell-wall scaffolding EXTENSIN (EXT) proteins that regulate de novo cell-wall formation and cell expansion. Since CEPs cleave EXTs and EXT-related proteins, acting as cell-wall-weakening agents, they may play a role in cell elongation. The Arabidopsis (Arabidopsis thaliana) genome encodes 3 CEPs (AtCPE1-AtCEP3). Here, we report that the genes encoding these 3 Arabidopsis CEPs are highly expressed in root-hair (RH) cell files. Single mutants have no evident abnormal RH phenotype, but atcep1-3 atcep3-2 and atcep1-3 atcep2-2 double mutants have longer RHs than wild-type (Wt) plants, suggesting that expression of AtCEPs in root trichoblasts restrains polar elongation of the RH. We provide evidence that the transcription factor NAC1 (petunia NAM and Arabidopsis ATAF1, ATAF2, and CUC2) activates AtCEPs expression in roots to limit RH growth. Chromatin immunoprecipitation indicates that NAC1 binds to the promoter of AtCEP1, AtCEP2, and, to a lower extent, AtCEP3 and may directly regulate their expression. Inducible NAC1 overexpression increases AtCEP1 and AtCEP2 transcript levels in roots and leads to reduced RH growth while the loss of function nac1-2 mutation reduces AtCEP1-AtCEP3 gene expression and enhances RH growth. Likewise, expression of a dominant chimeric NAC1-SRDX repressor construct leads to increased RH length. Finally, we show that RH cell walls in the atcep1-3 atcep3-2 double mutant have reduced levels of EXT deposition, suggesting that the defects in RH elongation are linked to alterations in EXT processing and accumulation. Our results support the involvement of AtCEPs in controlling RH polar growth through EXT processing and insolubilization at the cell wall.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Peptídeo Hidrolases/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Root hairs (RH) have become an important model system for studying plant growth and how plants modulate their growth in response to cell-intrinsic and environmental stimuli. Here, we will discuss recent advances in our understanding of the molecular mechanisms underlying the growth of Arabidopsis thaliana RH in the interface between responses to environmental cues (e.g. nutrients such as nitrates, phosphate and microorganism) and hormonal stimuli (e.g. auxin). RH growth is under the control of several transcription factors that are also under strong regulation at different levels. In this review we highlight recent new discoveries along these transcriptional pathways that may increase our capacity to enhance nutrient uptake by the roots in the context of abiotic stresses. We used text-mining capacities of the PlantConnectome database to generate the most updated view of RH growth in these complex biological contexts.
RESUMO
Plants exposed to freezing and above-freezing low temperatures must employ a variety of strategies to minimize fitness loss. There is a considerable knowledge gap regarding how mild low temperatures (around 10 °C) affect plant growth and developmental processes, even though the majority of the molecular mechanisms that plants use to adapt to extremely low temperatures are well understood. Root hairs (RH) have become a useful model system for studying how plants regulate their growth in response to both cell-intrinsic cues and environmental inputs. Here, we'll focus on recent advances in the molecular mechanisms underpinning Arabidopsis thaliana RH growth at mild low temperatures and how these discoveries may influence our understanding of nutrient sensing mechanisms by the roots. This highlights how intricately linked mechanisms are necessary for plant development to take place under specific circumstances and to produce a coherent response, even at the level of a single RH cell.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Temperatura , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Raízes de Plantas/metabolismo , Transdução de Sinais , Regulação da Expressão Gênica de PlantasRESUMO
Root hairs (RH) are excellent model systems for studying cell size and polarity since they elongate several hundred-fold their original size. Their tip growth is determined both by intrinsic and environmental signals. Although nutrient availability and temperature are key factors for a sustained plant growth, the molecular mechanisms underlying their sensing and downstream signaling pathways remain unclear. We use genetics to address the roles of the cell surface receptor kinase FERONIA (FER) and the nutrient sensing TOR Complex 1 (TORC) in RH growth. We identified that low temperature (10°C) triggers a strong RH elongation response in Arabidopsis thaliana involving FER and TORC. We found that FER is required to perceive limited nutrient availability caused by low temperature. FERONIA interacts with and activates TORC-downstream components to trigger RH growth. In addition, the small GTPase Rho of plants 2 (ROP2) is also involved in this RH growth response linking FER and TOR. We also found that limited nitrogen nutrient availability can mimic the RH growth response at 10°C in a NRT1.1-dependent manner. These results uncover a molecular mechanism by which a central hub composed by FER-ROP2-TORC is involved in the control of RH elongation under low temperature and nitrogen deficiency.