Biology subjects

Carignani, M.

Publications and source records attributed to Carignani, M..

3 recordsLinked to original sources

bioRxiv2024

Enhanced auxin signaling hub triggers root hair growth at moderate low temperature in Arabidopsis thaliana

Root hairs (RH) as a mixed tip- and non-tip growing protrusions that develop from root epidermal cells are important for nutrient and water uptake, root anchoring, and interaction with soil microorganisms. Although nutrient availability and temperature are critical interlinked factors for sustained plant growth, the molecular mechanisms underlying their sensing and downstream signaling pathways remain unclear. Here, we identified a moderate low temperature (10{degrees}C) condition that triggers a strong RH elongation response involving several molecular components of the auxin pathway. Then, we have determined that auxin biosynthesis carried out by YUCCAs/TAA1, the auxin transport conducted by PIN2/PIN4 and AUX1/PGP4, and the auxin signaling controlled by TIR1/AFB2 coupled to four specific ARFs (ARF6/ARF8 and ARF7/ARF19), are all crucial for the RH response at moderate low temperature. These results uncover the auxin pathway as one central hub under moderate low temperature in the roots to trigger RH growth. Our work highlights the importance of moderate low temperature stimulus as a complex nutritional signal from the media soil into the roots that may be fine-tuned for future biotechnological applications to enhance nutrient uptake.

plant biology↗

bioRxiv2023

NAC1 directs CEP1-CEP3 peptidase expression and decreases cell wall extensins linked to root hair growth in Arabidopsis

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 proteins (EXTs), which regulate de novo cell wall formation and cell expansion. Since CEPs are able to cleave EXTs and EXT-related proteins, acting as cell wall-weakening agents, they may play a role in cell elongation. Arabidopsis thaliana genome encodes three CEPs (AtCPE1-AtCEP3). Here we report that the three Arabidopsis CEPs, AtCEP1-AtCEP3, are highly expressed in root-hair cell files. Single mutants have no evident abnormal root-hair phenotype, but atcep1-3 atcep3-2 and atcep1-3 atcep2-2 double mutants have longer root hairs (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 activates AtCEPs expression in roots to limit RH growth. Chromatin immunoprecipitation indicates that NAC1 binds the promoter of AtCEP1, AtCEP2, and to a lower extent to AtCEP3 and may directly regulate their expression. Indeed, 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 atcep1-1 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. Taken together, our results support the involvement of AtCEPs in controlling RH polar growth through EXT-processing and insolubilization at the cell wall.

plant biology↗

bioRxiv2019

A cell surface O-glycosylated peptide, AGP21, acts on the brassinosteroid pathway and modulates root hair cell fate

Root hairs (RHs) develop from specialized epidermal cells called trichoblasts, whereas epidermal cells that lack RHs are known as atrichoblasts. The mechanism controlling root epidermal cell fate is only partially understood. Root epidermis cell fate is regulated by a transcription factor complex that promotes the expression of the homeodomain protein GLABRA 2 (GL2), which blocks RH development by inhibiting ROOT HAIR DEFECTIVE 6 (RHD6). Suppression of GL2 expression activates RHD6, a series of downstream TFs including ROOT HAIR DEFECTIVE 6 LIKE-4 (RSL4 [Yi et al. 2010]) and their target genes, and causes epidermal cells to develop into RHs. Brassinosteroids (BRs) influence root epidermis cell fate. In the absence of BRs, phosphorylated BIN2 (a Type-II GSK3-like kinase) inhibits a protein complex that directly downregulates GL2 [Chen et al. 2014]. Here, we show that the genetic and pharmacological perturbation of the arabinogalactan peptide (AG) AGP21 in Arabidopsis thaliana, triggers aberrant RH development, similar to that observed in plants with defective BR signaling. We reveal that an O-glycosylated AGP21 peptide, which is positively regulated by BZR1, a transcription factor activated by BR signaling, affects RH cell fate by altering GL2 expression in a BIN2-dependent manner. These results suggest that perturbation of a cell surface AGP disrupts BR responses and inhibits the downstream effect of BIN2 on the RH repressor GL2 in root epidermal cells. In addition, AGP21 also acts in a BR-independent, AGP-dependent mode that together with BIN2 signalling cascade controls RH cell fate. SignificanceIn the plant Arabidopsis thaliana, the root epidermis forms in an alternating pattern atrichoblasts with trichoblast cells that end up developing root hairs (RHs). Atrichoblast cell fate is directly promoted by the transcription factor GLABRA2 (GL2) while the lack of GL2 allows RH formation. The loss of AGP21 peptide triggers an abnormal RH cell fate in two contiguous cells in a similar manner as brassinosteroid (BRs) mutants. In the absence of BR signaling, BIN2 (a GSK3 like-kinase) in a phosphorylated state, downregulate GL2 expression to trigger RH cell fate. The absence of AGP21 is able to repress GL2 expression and activates the expression of RSL4 and EXP7 root hair proteins.

plant biology↗