Biology subjects

Eng, R. C.

Publications and source records attributed to Eng, R. C..

3 recordsLinked to original sources

bioRxiv2026

CESA7 and microtubules pattern complex secondary cell walls in explosive fruit

Secondary cell walls (SCW) constitute the most abundant form of renewable plant biomass and are major sinks for atmospheric carbon. Their highly ordered patterns underpin specialized cell functions. In Cardamine hirsuta, the geometry of a polarly localized SCW in fruit endocarp b (endb) cells determines the mechanics of explosive seed dispersal. Yet, the genetic control of SCW synthesis and patterning in these specialized cells remains poorly understood. Here we show that CELLULOSE SYNTHASE 7 (CESA7) is required to synthesize SCW cellulose in endb cells. While lignin and xylan deposition occurs independently of cellulose patterning in cesa7 endb SCWs, the final geometry and layered organization of wild-type endb SCWs depend on CESA7. Cellulose serves as a scaffold for the organized assembly of SCW polymers, thereby maintaining the precise SCW patterns observed in endb cells of fruits and metaxylem cells in roots. Cortical microtubules guide the patterned deposition of cellulose, lignin and xylan in endb cells, creating SCW-depleted domains along cell edges that produce the specific hinged SCW geometry. Disrupting microtubules abolished this pattern and prevented explosive coiling of the fruit valves. Our findings show that microtubules and CESA7 shape the form and function of endb SCWs in exploding seed pods.

plant biology↗

bioRxiv2024

Microtubule plus-end dynamics are tightly coupled to the turnover of the MOR1 polymerase

MOR1/XMAP215/Dis1/Stu2 family proteins function as polymerases that promote microtubule assembly through tubulin-interacting N-terminal tumor-overexpressed gene (TOG) domains. It remains unclear how the polymerase activity of these proteins is coordinated with their movement along the growing microtubule lattice. Previously, it was found that a L174F mutation in the N-terminal TOG domain of the 217 kDa Arabidopsis thaliana MICROTUBULE ORGANIZATION 1 (MOR1) protein impaired microtubule growth and shrinkage rates in a temperature-dependent manner. In this study, we used a homologous recombination strategy to generate stable transgenic lines expressing full-length MOR1 and mutant mor1-1L174F proteins tagged with the yellow fluorescent protein YPet. When expressed in mor1 mutant backgrounds, MOR1-3xYPet showed strong association with both the growing and shrinking microtubule plus ends, consistent with its involvement in both polymerization and depolymerization. By contrast, when expressed in a wild-type background, MOR1-3xYPet was redistributed along the microtubule lattice, microtubule growth rates were reduced, and plant growth was stunted. By quantifying fluorescence recovery after photobleaching, we confirmed that MOR1 has greater affinity for the plus end than the lattice. Exploiting the FRAP technique further, we identified a positive and linear correlation between microtubule polymerization rates and MOR1 turnover at the microtubule plus end. When microtubule growth rates were reduced in the mor1-1-YPet line by shifting the temperature from 21 to 30{degrees}C and for MOR1-3xYPet under taxol treatments, MOR1s turnover was delayed. In contrast, microtubule growth rates and MOR1 turnover were hastened at 30{degrees}C or after CRISPR/Cas9-mediated knock out of the CLASP protein. These findings support a new model whereby MOR1 has finite processivity on the microtubule, catalyzing a limited fixed number of tubulin additions before dissociation. HIGHLIGHTSMOR1 has high affinity for both growing and shrinking microtubule plus ends, consistent with a function in both polymerization and depolymerization events. MOR1 has greater affinity for microtubule plus ends than the lattice, and lattice binding associated with overexpression is detrimental to plant growth. MOR1 transiently associates with the microtubule plus end, the duration of which is tightly coupled with its polymerase activity.

cell biology↗

bioRxiv2023

Microtubule-mediated cell shape regulation contributes to efficient cell packing in Arabidopsis thaliana cotyledons

Recent advances have started to uncover the mechanisms involved in organ and cell shape regulation. However, organizational principles of epidermal cells in different tissues remain poorly understood. Here, we show that polygonal representations of cotyledon pavement cells (PCs) in Arabidopsis thaliana exhibit increasing irregularity in side lengths and internal vertex angles during early stages of development. While the shape of PCs in cotyledons is more complex than that of cells in the shoot apical meristem (SAM), the polygonal representations of these cells share similar irregularity of side length. Comparison of the surface cell area with the area of the regular polygons, having optimally spaced tri-cellular junctions, reveals suboptimal junction placement for coverage in cotyledons and SAM. We also found that cotyledons show increased packing density compared to the SAM, indicating that PCs forgo coverage of larger areas to potentially increase tissue stability. The identified shape irregularity and cell packing is associated with microtubule cytoskeleton. Our study provides a framework to analyze reasons and consequences of irregularity of polygonal shapes for biological as well as artificial shapes in larger organizational context. SummaryWe provide a polygonal cell representation in a tissue context and use it to draw conclusions about cell packing in epidermis of A. thaliana cotyledon.

developmental biology↗