Biology subjects

Bacic, A.

Publications and source records attributed to Bacic, A..

8 recordsLinked to original sources

bioRxiv2026

Developmental and regulatory logic of cannabis glandular trichomes resolved by single cell multiomics

Glandular trichomes of Cannabis sativa produce specialised metabolites including cannabinoids and terpenes, yet the cellular basis of trichome development and metabolic specialisation remains unresolved. Here we reconstruct the glandular trichome lineage within the C. sativa inflorescence using single-cell transcriptomics and chromatin accessibility profiling. We identify a continuous developmental trajectory from the protoderm, linking bulbous, sessile, and capitate-stalked trichomes, indicating that these morphologies represent sequential stages rather than distinct trichome types. We further identify a previously undescribed neck cell that shares a developmental origin with secretory disc cells before lineage bifurcation. Integration of chromatin accessibility with transcription factor (TF) binding reveals cell state specific regulatory programs coordinating neck cell development and specialised metabolism, redox homeostasis, and secretion in mature secretory disc cells. Methyl jasmonate elicitation induces extensive transcriptional and chromatin landscape reprogramming in mature secretory disc cells and transient repression of specialised metabolic pathways. Together, these findings provide a cell-resolved regulatory framework for glandular trichome development and function, revising prevailing models of trichome identity, maturation and defence associated metabolic regulation.

plant biology↗

bioRxiv2025

The Building Blocks of Early Land Plants: Glycosyltransferases and Cell Wall Architecture in the model liverwort Marchantia polymorpha

The liverwort Marchantia polymorpha has emerged as an important plant model for developmental studies and may become central to elucidate the complex process of cell wall polysaccharide biosynthesis. This study comprehensively analyses the composition and structure of cell wall glycans across eight different M. polymorpha tissue types. We show that while the cell walls largely mirror known land plant cell wall composition, they also exhibit some unique characteristics. For example, -(1,5)-arabinan was prominently present in the sporophyte tissue, which may indicate a specialised role in this life stage. Furthermore, M. polymorpha cell walls displayed a remarkably low overall pectin content, yet the abundance of pectic arabinan in sporophytes hint at its putative role in the evolution and complexity of spermatophyte cell walls. Through comparative analyses of glycosyltransferase (GT) families across plant species, we found that M. polymorpha has a diversified GT repertoire compared for example, to the model plant Arabidopsis thaliana, indicating uniqueness in its cell wall biosynthesis pathways. To support research underpinning cell wall biosynthesis, we developed a Gateway compatible compendium of 93 M. polymorpha GTs, providing a valuable resource for genetic and functional studies. Our study thus works as a foundation to drive new insights into cell wall evolution, structure and function across the plant kingdom.

plant biology↗

bioRxiv2025

Seagrass arabinogalactan-proteins: Are they important for adaptation to the marine environment?

During the late cretaceous period several lineages of angiosperm plants transitioned from land to the sea by successfully adapting to life in salt water, forming the polyphyletic group of seagrasses. Today, four seagrass families inhabit coastal systems and are deeply intertwined with health and welfare of these ecosystems. Adaptation to the ocean environment included changes in the composition of plant cell walls and associated glycoproteins. We have asked the question whether or not there is a convergent and similar arabinogalactan-protein glycan repertoire in all seagrasses, given initial findings of arabinogalactan-proteins with unique features in the well-studied eelgrass, Zostera marina. We isolated and characterized arabinogalactan-proteins from seven species covering the four major seagrass families using carbohydrate analysis and glycan immunoassays, along with a bioinformatic search for relevant gene pathways in newly published seagrass genomes and transcriptomes. Glycan parts of all seagrass arabinogalactan-proteins shared a high proportion of 1,4-linked glucuronic acids and terminal 4-O-methyl glucuronic acid residues. Trait-based dendrograms generated to inform phylogenetic-relatedness showed there was no phylogenetic signal among seagrass families and arabinogalactan-protein features. Transcriptomic datasets from Cymodocea nodosa and Thalassia hemprichii growing under hypersaline conditions showed an upregulation of enzymes involved in 4O-methylation and glucuronic acid transfer. We therefore conclude that environmental factors, especially salinity with higher monovalent ion concentration, influence seagrass arabinogalactan-proteins structure more intensely than phylogenetic history.

plant biology↗

bioRxiv2023

Cell wall pectic β-1,4-galactan contributes to increased plant freezing tolerance induced by cold acclimation

Subzero temperatures are often lethal to plants. Many temperate plants have a mechanism called cold acclimation that allows them to sense a drop in temperature and prepare for freezing stress through accumulation of soluble sugars and cryoprotective proteins. Plant cells are surrounded by a cell wall and as ice formation primarily occurs in the extracellular matrix (the apoplast), cell wall properties are important for plant freezing tolerance. Although previous studies have shown that the amounts of constituent sugars of the cell wall, in particular those present in pectic polysaccharides, are altered by cold acclimation, the significance of this change during cold acclimation has not been clarified. We found that {beta}-1,4-galactan, which forms neutral side chains of pectin, accumulates in the cell walls of Arabidopsis and various freezing tolerant vegetables during cold acclimation. The gals1 gals2 gals3 triple mutant, which has reduced {beta}-1,4-galactan in the cell wall, exhibited reduced freezing tolerance compared with wild-type Arabidopsis during initial stages of cold acclimation. Expression of genes involved in the galactan biosynthesis pathway such as GALACTAN SYNTHASES and UDP-glucose 4-epimerases were induced during cold acclimation in Arabidopsis explaining galactan accumulation. Cold acclimation resulted in a decrease in extensibility and an increase in rigidity of the cell wall in the wild type, whereas these changes were not observed in the gals1 gals2 gals3 triple mutant. These results indicate that the accumulation of pectic {beta}-1,4-galactan contributes to acquired freezing tolerance by cold acclimation via changes in cell wall mechanical properties.

plant biology↗

bioRxiv2022

DEFECTIVE KERNEL1 (DEK1) regulates cellulose synthesis and affects primary cell wall mechanics

The cell wall is one of the defining features of plants, controlling cell shape, regulating growth dynamics and hydraulic conductivity, as well as mediating plants interactions with both the external and internal environments. Here we report that a putative mechanosensitive Cys-protease DEFECTIVE KERNEL1 (DEK1) interacts with cell wall integrity (CWI) pathways and regulation of cellulose synthesis. Our results indicate that DEK1 is an important regulator of cellulose synthesis in epidermal tissue of Arabidopsis thaliana cotyledons during early post-embryonic development. DEK1 is involved in regulation of cellulose synthase complexes (CSCs) by modifying their biosynthetic properties, possibly through interactions with various cellulose synthase regulatory proteins. Mechanical properties of the primary cell wall are altered in DEK1 modulated lines supporting a role in maintenance of CWI. DEK1 affects stiffness of the cell wall and thickness of the cellulose microfibrils bundles in epidermal cell walls of cotyledons.

plant biology↗

bioRxiv2021

A Phytochrome B-PIF4-MYC2 Module Tunes Secondary Cell Wall Thickening in Response to Shaded Lighting

Secondary cell walls (SCW) in stem xylem cells provide mechanical strength and structural support for growth. SCW thickening is light- regulated and varies under different light growth conditions. Our previous study revealed that blue light enhances SCW thickening through the activity of MYC2 directed by CRYPTOCHROME1 (CRY1) signaling in stem xylary fiber cells. In this study, we demonstrate that the low ratio of red: far-red light (R:FR) of the shaded light condition inhibits SCW thickening in the inflorescence stem of Arabidopsis. Phytochrome B (PHYB) plays a dominant role in perceiving the R:FR balance. Under white and red-light conditions, phyB mutants display thinner SCWs in xylary fibers, but thicker SCWs are deposited in the PHYTOCHROME INTERACTING FACTORS (PIFs) quadruple mutant pif1pif3pif4pif5 (pifq), suggesting involvement of the PHYB-PIFs signaling module in regulating SCW thickening. Interaction of PIF4 with MYC2 affects MYC2 localization in nuclei and inhibits its transactivation activity on the NST1 promoter. Shade conditions mediate the PIF4 interaction with MYC2 to regulate SCW thickening. Genetic analysis confirms that the regulation of SCW thickening by PIFs is dependent on MYC2 function. Together, these data reveal a molecular mechanism for the effect of shaded light inhibition on SCW thickening in stems of Arabidopsis.

plant biology↗

bioRxiv2020

Targeted mutation of barley (1,3;1,4)-β-glucan synthases reveals complex relationships between the storage and cell wall polysaccharide content

Barley (Hordeum vulgare L) grain is comparatively rich in (1,3;1,4)-{beta}-glucan, a source of fermentable dietary fibre that protects against various human health conditions. However, low grain (1,3;1,4)-{beta}-glucan content is preferred for brewing and distilling. We took a reverse genetics approach, using CRISPR/Cas9 to generate mutations in members of the Cellulose synthase-like (Csl) gene superfamily that encode known (HvCslF6 and HvCslH1) and putative (HvCslF3 and HvCslF9) (1,3;1,4)-{beta}-glucan synthases. Resultant mutations ranged from single amino acid (aa) substitutions to frameshift mutations causing premature stop codons, and led to specific differences in grain morphology, composition and (1,3;1,4)-{beta}-glucan content. (1,3;1,4)-{beta}-Glucan was absent in the grain of cslf6 knock-out lines whereas cslf9 knock-out lines had similar (1,3;1,4)-{beta}-glucan content to WT. However, cslf9 mutants showed changes in the abundance of other cell wall-related monosaccharides compared to WT. Thousand grain weight (TGW), grain length, width and surface area were altered in cslf6 knock-outs and to a lesser extent TGW in cslf9 knock-outs. cslf3 and cslh1 mutants had no effect on grain (1,3;1,4)-{beta}-glucan content. Our data indicate that multiple members of the CslF/H family fulfil important functions during grain development but, with the exception of HvCslF6, do not impact the abundance of (1,3;1,4)-{beta}-glucan in mature grain.

plant biology↗

bioRxiv2019

Integrative Multi-Omics Analysis of Barley Genotypes Shows Differential Salt-Induced Osmotic Barriers and Response Phases Among Rootzones

The mechanisms underlying rootzone-localised responses to salinity stress during early stage of barley development remains fragmentary and elusive. Here, we performed a comprehensive detection of the multi-root-omes (transcriptomes, metabolomes, lipidomes) of a domesticated barley cultivar (Clipper) and a landrace (Sahara) with seedling root growth maintained and restricted in response to salt stress, respectively. Novel generalized linear models were designed to determine differentially expressed genes (DEG) or abundant metabolites (DAM) specific to salt treatments, genotypes, or rootzones (meristematic Z1, elongation Z2, maturation Z3). Based on pathway over-representation of the DEG and DAM, phenylpropanoid biosynthesis is the most statistically over-represented biological pathways among all salinity responses observed. Together with the histological evidence, an intense salt-induced lignin impregnation was found only at the stelic cell wall of Clipper Z2, comparing to a unique elevation of suberin deposition across Sahara Z2. This suggests two differential salt-induced modulations of apoplastic flow between the genotypes. Based on global correlation network construction of the DEG and DAM, callose deposition that potentially adjusted the symplastic flow in roots was almost independent of salinity in rootzones of Clipper, but was markedly decreased in that of Sahara. Through closer examinations of molecular and hormonal clues, we further demonstrate that the salinity response in rootzones of Clipper were mostly at recovery phase, comparing to Sahara with rootzones retained at quiescence. Taken together, we propose that two distinctive salt tolerance mechanisms could exist in Clipper (growth-sustaining) and Sahara (salt-shielding), providing important clues for improving crop plasticity to cope with the deteriorating global salinization of soil.

plant biology↗