Biology subjects

Kessler, S. A.

Publications and source records attributed to Kessler, S. A..

5 recordsLinked to original sources

bioRxiv2025

MLO-mediated Ca2+ influx regulates root hair tip growth in Arabidopsis

O_LIRoot hair tip-growth involves coordinated Ca2+ and ROS signaling to promote growth while maintaining tip integrity. MILDEW RESISTANCE LOCUS-O (MLO) proteins act downstream of FERONIA (FER) receptor-like kinases in pollen tubes and synergids to regulate calcium dynamics. This study uses a constitutively active MLO (faNTA) to identify a new role for the FER/MLO signaling module in regulating [Ca2+]cyt oscillations in growing root hairs. C_LIO_LIfaNTA bypasses FER signaling in root hairs, complementing not only the previously reported fer-4 root hair bursting phenotype, but also the complete loss of polarity in spherical root hairs. This complementation correlates with the restoration of tip-focused [Ca2+]cyt oscillations that are disrupted in fer mutants, suggesting that MLOs are involved in regulating [Ca2+]cyt dynamics in growing root hairs. C_LIO_LIMLO15 was identified as a regulator of root hair tip-growth based on disrupted root hair growth and [Ca2+]cyt signatures in mlo15-4. We also link the FER/MLO module to ROS accumulation by showing that faNTA is sufficient to restore ROS levels in fer-4 root hairs and that ROS levels are decreased in mlo15-4 root hairs. C_LIO_LIWe propose that MLOs act downstream of FER to mediate Ca2+ influx and promote ROS production in order to regulate root hair tip-growth. C_LI Plain Language SummaryRoot hairs are important for expanding the surface area of the root for optimal absorption of water and minerals. A FERONIA/MLO signal module promotes tip growth in these specialized cells by regulating calcium and reactive oxygen species accumulation. Understanding tip growth mechanisms may help optimize root responses to environmental challenges.

plant biology↗

bioRxiv2025

ROS regulation of stigma papillae growth and maturation in Arabidopsis thaliana

Highly specialized stigma papillae cells play a critical role in plant reproduction. Their main purpose is to catch and interact with pollen, to mediate compatibility responses, to regulate pollen germination, and to guide pollen tubes to the transmitting tract so that the sperm cells carried in the pollen can be delivered to the female gametophyte to achieve double fertilization. In Arabidopsis thaliana, the stigma consists of single-celled stigma papillae that emerge from the apex of the fused carpels. Despite their critical function in plant reproduction, the molecular mechanisms that govern growth and maturation of stigma papillae remain poorly understood. Reactive Oxygen Species (ROS) have been implicated in stigma receptivity, but their roles in papillae development are less explored. Here we show that reactive oxygen species (ROS) also play different roles in stigma papillae development, with superoxide accumulating during the initiation and growth phase and hydrogen peroxide accumulating in mature papillae that are receptive to pollen. Reducing superoxide levels in the stigma by pharmacological treatments or over-expressing superoxide dismutase enzymes under an early stigma promoter inhibited stigma papillae growth, suggesting that ROS homeostasis is critical to papillae growth and differentiation for optimal pollination. Statements and DeclarationsThe authors declare no competing interests

plant biology↗

bioRxiv2025

Anisotropic diffuse growth in Arabidopsis stigma papillae

In angiosperms, the stigma is the first point of contact between the pollen (male) and pistil (female) during pollination. The stigma facilitates pollen capture and adhesion, compatibility responses, pollen germination, and pollen tube guidance to the transmitting tract. In Arabidopsis thaliana, the stigma is composed of single-celled stigma papillae that initiate from the apex of the carpels. Despite their critical function in plant reproduction, little is known about the cell and molecular mechanisms that govern stigma papillae growth and development. Using morphometric analysis of stigma papillae growth during different stages of floral development, we show that Arabidopsis stigma papillae grow via an anisotropic diffuse growth mechanism. Consistent with this conclusion, vegetative anisotropic growth mutants with defective microtubule and cellulose microfibril organization also have compromised stigma papillae growth.

plant biology↗

bioRxiv2019

Redistribution of NORTIA in response to pollen tube arrival facilitates fertilization in Arabidopsis thaliana

During gamete delivery in Arabidopsis thaliana, intercellular communication between the attracted pollen tube and the receptive synergid cell leads to subcellular events in both cells culminating in the rupture of the tip-growing pollen tube and release of the sperm cells to achieve double fertilization. Live imaging of pollen tube reception revealed dynamic subcellular changes that occur in the female synergid cells. Pollen tube arrival triggers the trafficking of NORTIA (NTA) MLO protein from Golgi-associated compartments and the accumulation of endosomes at or near the synergid filiform apparatus, a membrane-rich region that acts as the site of communication between the pollen tube and synergids. Domain swaps and site-directed mutagenesis reveal that NTAs C-terminal cytoplasmic tail with its calmodulin-binding domain influences the subcellular localization and function of NTA in pollen tube reception and that accumulation of NTA at the filiform apparatus is necessary and sufficient for MLO function in pollen tube reception.

plant biology↗

bioRxiv2018

A Genome-Wide Association Study Reveals a Novel Regulator of Ovule Number and Fertility in Arabidopsis thaliana

Ovules contain the female gametophytes which are fertilized during pollination to initiate seed development. Thus, the number of ovules that are produced during flower development is an important determinant of seed crop yield and plant fitness. Mutants with pleiotropic effects on development often alter the number of ovules, but specific regulators of ovule number have been difficult to identify in traditional mutant screens. We used natural variation in Arabidopsis accessions to identify new genes involved in the regulation of ovule number. The ovule numbers per flower of 189 Arabidopsis accessions were determined and found to have broad phenotypic variation that ranged from 39 ovules to 84 ovules per pistil. Genome-Wide Association tests revealed several genomic regions that are associated with ovule number. T-DNA insertion lines in candidate genes from the most significantly associated loci were screened for ovule number phenotypes. The NEW ENHANCER of ROOT DWARFISM (NERD1) gene was found to have pleiotropic effects on plant fertility that include regulation of ovule number and both male and female gametophyte development. Overexpression of NERD1 increased ovule number per fruit in a background-dependent manner and more than doubled the total number of flowers produced in all backgrounds tested, indicating that manipulation of NERD1 levels can be used to increase plant productivity.\n\nAuthor SummaryOvules are the precursors of seeds in flowering plants. Each ovule contains an egg cell and a central cell that fuse with two sperm cells during double fertilization to generate seeds containing an embryo and endosperm. The number of ovules produced during flower development determines the maximum number of seeds that can be produced by a flower. In this paper, we used natural variation in Arabidopsis thaliana accessions to identify regions of the genome that are associated with ovule number. Polymorphisms in the plant-specific NERD1 gene on chromosome 3 were significantly associated with ovule number. Mutant and overexpression analyses revealed that NERD1 is a positive regulator of ovule number, lateral branching, and flower number in Arabidopsis. Manipulation of NERD1 expression levels could potentially be used to increase yield in crop plants.

plant biology↗