Biology subjects

Hussey, P. J.

Publications and source records attributed to Hussey, P. J..

5 recordsLinked to original sources

bioRxiv2024

A Rab-Kinesin12-Fused kinase module couples vesicle delivery and phragmoplast remodelling during cytokinesis in Arabidopsis

Cytokinesis is a key process in the development of multicellular organisms, through both formative and proliferative divisions. In land plants, successful cytokinesis requires precise targeting of Golgi-derived vesicles to the future division plane by the phragmoplast, a cytoskeletal structure that undergoes continuous remodelling. Endomembrane trafficking and phragmoplast remodelling are tightly coupled, indicating the existence of active crosstalk. However, although many molecular regulators of membrane trafficking and cytoskeletal organisation are known, it remains poorly understood how these processes are co-ordinated. Here, we describe a regulatory module consisting of the membrane-associated GTPase RAB-A2a, cytoskeleton-associated Class II Kinesin-12s, and the Fused kinase orthologue TIO. We provide evidence that the interaction between these molecules at the midzone is essential for cytokinesis in Arabidopsis through simultaneously targeting vesicles to the midzone and coupling phragmoplast remodelling to vesicle delivery.

plant biology↗

bioRxiv2022

TraB is a novel component of the ER-Mitochondria contact site (EMCS) with dual roles in ER-Mitochondrial tethering and mitophagy

ER-mitochondria contact sites (EMCSs) are important for mitochondrial function. Here, we have identified a novel eukaryotic EMCS complex, comprising a family of uncharacterised mitochondrial outer-membrane proteins, TraB1 and the ER protein, VAP27-1. In Arabidopsis, there are two TraB1 isoforms and the trab1a/trab1b double mutant exhibits abnormal mitochondrial morphology, strong starch accumulation and impaired energy metabolism, indicating that these proteins are essential for normal mitochondrial function. Moreover, TraB1 proteins also interact with ATG8 in order to regulate mitochondrial degradation (mitophagy). The turnover of depolarised mitochondria is significantly reduced in both trab1a/b and VAP27 mutants (vap27-1/3/4/6) under mitochondrial stress conditions, with an increased population of dysfunctional mitochondria present in the cytoplasm. Consequently, plant recovery after stress is significantly perturbed. A similar phenotype is found in both autophagy mutants (atg5 and atg7), suggesting that TraB1 regulated mitophagy and ER-mitochondrial tethering are two closely related processes, necessary for normal mitochondrial function. Taken together, we ascribe a dual role to TraB1 which is a novel component of the EMCS complex in eukaryotes, regulating both tethering of the mitochondria to the ER and mitophagy.

cell biology↗

bioRxiv2021

A NET4-RabG3 couple mediate the link between actin and the tonoplast and is essential for normal actin cytoskeletal remodelling in stomatal closure to flg22

Members of the NETWORKED (NET) family are involved in actin-membrane interactions. They tether the cells plasma membrane (PM) to the actin network. Moreover, in a similar manner, they are also involved in the tethering of membrane bound organelles to the actin cytoskeleton; the endoplasmic reticulum (ER) and the ER to the PM. This raises the question as to whether NET proteins are involved in actin cytoskeletal remodelling. Here we show that two members of the NET family, NET4A and NET4B, are essential for normal guard cell actin reorganization, which is a process critical for stomatal closure in plant immunity. NET4 proteins interact with F-actin and with members of the Rab7 GTPase RABG3 family through two distinct domains, allowing for simultaneous localization to actin filaments and the tonoplast. NET4 proteins interact with GTP-bound, active RABG3 members, suggesting their function as downstream effectors. We also show that RABG3b is critical for stomatal closure induced by microbial patterns. Taken together, we conclude that the actin cytoskeletal remodelling during stomatal closure depends on a molecular link between actin filaments and the tonoplast, which is mediated by the NET4-RABG3b interaction. We propose that stomatal closure to microbial patterns involves the coordinated action of immune signalling events and proper actin cytoskeletal remodelling.

plant biology↗

bioRxiv2019

A specific exocytic pathway is essential for polarization of PIN proteins in the establishment and maintenance of auxin gradients.

O_LIThe plant hormone auxin and its directional intercellular transport plays a major role in diverse aspects of plant growth and development. The establishment of auxin gradients in plants requires asymmetric distribution of members of the auxin efflux carrier PIN-FORMED (PIN) protein family to the plasma membrane. An endocytic pathway regulates the recycling of PIN proteins between the plasma membrane and endosomes, providing a mechanism for dynamic localization. C_LIO_LIN-ethylmaleimide-sensitive factor adaptor protein receptors (SNAP receptors, SNAREs) mediate fusion between vesicles and target membranes and are classed as Q- or R-SNAREs based on their sequence. We analysed gain- and loss-of-function mutants, dominant negative transgenics and protein localization of the Arabidopsis R-SNARE VAMP714 to understand its function. C_LIO_LIWe demonstrate that VAMP714 is essential for the insertion of PINs into the plasmamembrane, for polar auxin transport, and for root gravitropism and morphogenesis. VAMP714 gene expression is upregulated by auxin, and the VAMP714 protein co-localizes with ER and Golgi vesicles and with PIN proteins at the plasma membrane. C_LIO_LIIt is proposed that VAMP714 mediates the delivery of PIN-carrying vesicles to the plasma membrane, and that this forms part of a positive regulatory loop in which auxin activates a VAMP714-dependent PIN/auxin transport system to control development. C_LI

plant biology↗

bioRxiv2017

Epidermal expression of a sterol biosynthesis gene regulates root growth by a non-cell autonomous mechanism in Arabidopsis

The epidermis has been hypothesized to play a signalling role during plant development. One class of mutants showing defects in signal transduction and radial patterning are those in sterol biosynthesis. The expectation is that sterol biosynthesis is a constitutive cell-autonomous process for the maintenance of basic cellular functions. The HYDRA1 (HYD1) gene of Arabidopsis encodes an essential sterol {Delta}8-{Delta}7 isomerase, and although hyd1 mutant seedlings are defective in radial patterning of several tissues, we show that the HYD1 gene is expressed primarily in the root epidermis. Cell type-specific transgenic activation of HYD1 transcription reveals that HYD1 expression in the epidermis of hyd1 null mutants is sufficient to rescue root patterning and growth. Unexpectedly, expression of HYD1 in the vascular tissues and root meristem, though not endodermis or pericycle, also leads to phenotypic rescue. Phenotypic rescue is associated with rescued patterning of the PIN1 and PIN2 auxin efflux carriers. The importance of the epidermis is in part due to its role as a site for tissue-specific sterol biosynthesis, and auxin is a candidate for a non-cell autonomous signal.

plant biology↗