Biology subjects

Meier, I.

Publications and source records attributed to Meier, I..

4 recordsLinked to original sources

bioRxiv2026

Nuclear basket localized proteasomes maintain circadian period through nuclear TOC1 proteolysis

Post-translational control of circadian period can involve changes in protein intracellular localization to affect clock function. Many clock proteins rely on a nuclear presence for their activity. As the primary gateway regulating the movement of molecules between the cytosol and the nucleus, the nuclear pore may assist in circadian system maintenance. We describe roles for the nuclear basket proteins, NUA and NUP136, in the maintenance of Arabidopsis circadian period, through effects on the stability of the core clock protein, TOC1. The circadian period of nua and nup136 mutants is significantly longer than that of wildtype plants. We show that NUP136 interacts with NUA, proteasome components and TOC1 in vivo, recruiting them to the inner nuclear rim. TOC1 interaction with the NUP136-NUA complex leads to a proteasome-dependent degradation of TOC1. Loss of NUP136 or NUA disrupts this regulatory environment, leading to aberrant nuclear TOC1 accumulation and consequent lengthening of circadian period. Our work thus identifies nuclear basket-localized proteasomes as key to the maintenance of circadian period.

plant biology↗

bioRxiv2022

Biosphere functional integrity for people and Planet

Defining a safe and just biosphere space requires a synthetic scaleable measure of biosphere functional integrity to secure Natures Contributions to People (NCP). Using a systematic review of 153 peer-reviewed studies we estimated the minimum level of functional integrity needed to secure multiple critical NCP, including pollination, pest and disease control, water quality regulation, soil protection, recreation and natural hazards mitigation in human-modified landscapes. We characterise functional integrity by the quantity, quality and spatial configuration of (semi-)natural habitat within any landscape. We find that at least 20-25% of structurally complex and biologically diverse (semi-)natural habitat in each 1 km2 of land area is needed to maintain the supply of multiple NCP simultaneously. Exact quantity, quality and spatial configuration required is dependent on local context, and may differ for individual NCP. Today, about 50-60% of human-modified lands have less than 10% and 20% (semi-)natural habitat per 1 km2 respectively. These areas require immediate attention to regenerate functional integrity in order to secure ecological functioning in those landscapes.

ecology↗

bioRxiv2020

Vegetative nuclear positioning is required for calcium and ROS signaling in Arabidopsis pollen tubes

Efficient transport and delivery of sperm cells (SCs) is vital for angiosperm plant fertility. In Arabidopsis thaliana, SCs are transported through the growing pollen tube by a connection with the vegetative nucleus (VN). During pollen tube growth, the VN leads the way and maintains a fixed distance from the pollen tube tip, while the SCs lag behind the VN. Upon reception at the ovule, the pollen tube bursts and the SCs are released for fertilization. In pollen tubes of Arabidopsis mutants wit12 and wifi, deficient in the outer nuclear membrane component of a plant LINC complex, the SCs precede the VN and the VN falls behind. Subsequently, pollen tubes frequently fail to burst upon reception. In this study, we sought to determine if the pollen tube reception defect observed in wit12 and wifi is due to decreased sensitivity to reactive oxygen species (ROS). Here we show that wit12 and wifi are hyposensitive to exogenous H2O2, and that this hyposensitivity is correlated with decreased proximity of the VN to the pollen tube tip. Additionally, we report the first instance of nuclear Ca2+ spikes in growing pollen tubes, which are disrupted in the wit12 mutant. In the wit12 mutant, nuclear Ca2+ spikes are reduced in response to exogenous ROS, but these spikes are not correlated with pollen tube burst. This study finds that VN proximity to the pollen tube tip is required for both response to exogenous ROS, as well as internal nuclear Ca2+ fluctuations. SummaryMutants deficient in outer nuclear membrane proteins display defects in reactive oxygen species-induced pollen tube burst and nuclear Ca2+ signatures that correlate with the position of the vegetative nucleus.

plant biology↗

bioRxiv2019

Establishing the role of SINE proteins in regulating stomatal dynamics in Arabidopsis thaliana

Stomatal movement, which regulates gas exchange in plants, is controlled by a variety of environmental factors, including biotic and abiotic stresses. The stress hormone ABA initiates a signaling cascade, which leads to increased H2O2 and Ca2+ levels and F-actin reorganization, but the mechanism of, and connection between, these events is unclear. SINE1, an outer nuclear envelope component of a plant Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, associates with F-actin and is, along with its paralog SINE2, expressed in guard cells. Here, we have determined that Arabidopsis SINE1 and SINE2 play an important role in stomatal regulation. We show that SINE1 and SINE2 are required for stomatal opening and closing. Loss of SINE1 or SINE2 results in ABA hyposensitivity and impaired stomatal dynamics but does not affect stomatal closure induced by the bacterial elicitor flg22. The ABA-induced stomatal closure phenotype is, in part, attributed to impairments in Ca2+ and F-actin regulation. Together, the data suggest that SINE1 and SINE2 act downstream of ABA but upstream of Ca2+ and F-actin. While there is a large degree of functional overlap between the two proteins, there are also critical differences. Our study makes an unanticipated connection between stomatal regulation and a novel class of nuclear envelope proteins, and adds two new players to the increasingly complex system of guard cell regulation.

plant biology↗