Biology subjects

Sedelnikova, O.

Publications and source records attributed to Sedelnikova, O..

4 recordsLinked to original sources

bioRxiv2024

Single-cell resolved differentiation of pre-Kranz anatomy in maize leaf primordia

Typical C4 plants such as maize possess highly optimized Kranz-type leaf anatomy, whereby concentric wreaths of mesophyll and bundle sheath cells surround closely spaced veins. The veins and the cells that surround them are derived from the middle ground meristem (mGM) through processes that are as yet undefined. Here we distinguished the active zone of vascular development within early leaf primordia, and used comparative transcriptomics of sub-sectioned maize and rice primordia to identify cohorts of genes likely involved in early Kranz development. Leveraging single-nucleus RNA sequencing (snRNA-seq) we then explored the cell heterogeneity and developmental trajectories within single maize leaf primordia. Assisted by in situ hybridization, cell clusters of mGM and procambium were identified, with candidate marker genes showing different yet inter-related expression patterns. Localization of the vascular marker ZmSHR1 was preceded by that of ZmEREB161 and ZmEREB114 in terms of procambium initiation. Potential subclusters of bundle sheath cells and different layer of mesophyll cells were depicted from developing cells toward the tip of sub-sectioned maize primordia. Collectively our results identify potential mGM derived or procambium localized Kranz regulators and provide resources for investigating leaf vein development in maize and rice, at sub-primordium and single-cell resolution.

plant biology↗

bioRxiv2024

Spatial transcriptomics reveals distinct lineage identities for major and minor vein initiation during maize leaf development

Leaves of flowering plants are characterised by diverse venation patterns. Patterning begins with the selection of vein-forming procambial initial cells from within the ground meristem of a developing leaf, a process which is considered to be auxin-dependent, and continues until veins are anatomically differentiated with functional xylem and phloem. At present, the mechanisms responsible for leaf venation patterning are primarily characterized in the model eudicot Arabidopsis thaliana which displays a reticulate venation network. However, evidence suggests that vein development may proceed via a different mechanism in monocot leaves where venation patterning is parallel. Here, we employed Molecular Cartography, a multiplexed in situ hybridization technique, to analyse the spatiotemporal localisation of a subset of auxin related genes and candidate regulators of vein patterning in maize leaves. We show how different combinations of auxin influx and efflux transporters are recruited during leaf and vein specification, and how major and minor vein ranks develop with distinct identities. The localisation of the procambial marker PIN1a and the spatial arrangement of procambial initial cells that give rise to major and minor vein ranks further suggests that vein spacing is pre-patterned across the medio-lateral leaf axis prior to accumulation of the PIN1a auxin transporter. In contrast, patterning in the adaxial-abaxial axis occurs progressively, with markers of xylem and phloem gradually becoming polarised as differentiation proceeds. Collectively our data suggest that both lineage- and position-based mechanisms may underpin vein patterning in maize leaves. SIGNIFICANCE STATEMENTDuring the development of multicellular organisms specialized cell-types differentiate from pluripotent stem cells, with cell identity acquired via lineage- or position-based mechanisms. In plants, most organs develop post-embryogenesis and as such developmental processes are influenced by the external environment. To adapt to different environmental contexts and yet still form recognizable structures, position-based differentiation mechanisms are deployed in which cells adopt a certain fate depending on the activity of neighbouring cells. Such is the prevalence of position-based mechanisms in plant development that a role for lineage is rarely contemplated. Here we show that stem cells which give rise to different vein types in maize leaves are transcriptionally distinct, possibly reflecting a role for lineage-based mechanisms in the differentiation of leaf veins.

plant biology↗

bioRxiv2023

THE WIP6 TRANSCRIPTION FACTOR TOO MANY LATERALS SPECIFIES VEIN TYPE IN C4 AND C3 GRASS LEAVES

Grass leaves are invariantly strap shaped with an elongated distal blade and a proximal sheath that wraps around the stem. Underpinning this uniform shape is a scaffold of leaf veins, most of which extend in parallel lines along the proximo-distal leaf axis. Differences between species are apparent both in the types of veins that develop and in the spacing between them across the medio-lateral leaf axis. A prominent engineering goal is to increase vein density and the proportion of bundle sheath cells surrounding the veins in leaves of C3 photosynthesizing species such as rice, in order to facilitate introduction of the more efficient C4 photosynthetic pathway. Here we discover that the WIP6 zinc finger transcription factor TOO MANY LATERALS (TML) specifies vein rank in both maize (C4) and rice (C3), species with distinct venation patterns. Loss of function tml mutations lead to the development of large lateral veins in positions normally occupied by smaller intermediate veins. The spatial localization of TML transcripts in wild-type leaves is consistent with a role in suppressing lateral vein formation in procambial cells that develop intermediate veins, specifically the class of intermediate veins that extend from the leaf blade into the leaf sheath. Attempts to manipulate TML function in rice were unsuccessful because transgene expression was silenced, suggesting that precise spatial and temporal regulation of TML expression is essential during the regeneration of shoot tissue from callus. Given that transcriptome analysis demonstrated altered profiles of genes associated with cytokinin and auxin signaling in loss of function maize mutants, the necessity for tight regulation of TML gene expression could be an indirect consequence of hormonal inbalances as opposed to ectopic activity of a specific downstream target. Importantly, however, loss of function mutants in rice display increased vascular and bundle sheath cell occupancy in the leaf. Collectively this work provides an understanding of how vein rank is specified in grass leaves and a first step towards an anatomical chassis for C4 engineering in rice.

plant biology↗

bioRxiv2022

Mutations in NAKED-ENDOSPERM IDD genes reveal functional interactions with SCARECROW and a maternal influence on leaf patterning in C4 grasses

Leaves comprise a number of different cell-types that are patterned in the context of either the epidermal or inner cell layers. In grass leaves, two distinct anatomies develop in the inner leaf tissues depending on whether the leaf carries out C3 or C4 photosynthesis. In both cases a series of parallel veins develops that extends from the leaf base to the tip but in ancestral C3 species veins are separated by a greater number of intervening mesophyll cells than in derived C4 species. We have previously demonstrated that the GRAS transcription factor SCARECROW (SCR) regulates the number of photosynthetic mesophyll cells that form between veins in the leaves of the C4 species maize, whereas it regulates the formation of stomata in the epidermal leaf layer in the C3 species rice. Here we show that SCR is required for inner leaf patterning in the C4 species Setaria viridis but in this species the presumed ancestral stomatal patterning role is also retained. Through a comparative mutant analysis between maize, setaria and rice we further demonstrate that loss of NAKED-ENDOSPERM (NKD) INDETERMINATE DOMAIN (IDD) protein function exacerbates loss of function scr phenotypes in the inner leaf tissues of maize and setaria but not rice. Specifically, in both setaria and maize, scr;nkd mutants exhibit an increased proportion of fused veins with no intervening mesophyll cells, whereas inner leaf tissues are patterned normally in scr;nkd mutants of rice. Thus, combined action of SCR and NKD may control how many mesophyll cells are specified between veins in the leaves of C4 but not C3 grasses. Finally, we identified a maternal effect in maize in which maternally derived NKD can affect patterning of cells in leaf primordia that are initiated during embryogenesis. Together our results provide insight into the evolution of cell patterning in grass leaves, demonstrate a novel patterning role for IDD genes in C4 leaves and suggest that NKD can influence embryonic leaf development non-cell autonomously from the surrounding maternal tissue. Summary statementMutations in NKD IDD genes enhance loss of function scr phenotypes in the leaves of C4 grasses maize and Setaria viridis but not in the C3 grass rice, and reveal a maternal effect on cell-type patterning in leaves that are initiated during embryogenesis.

plant biology↗