Abstract

TALK 1

Name: Feline Lindhount

Affiliation: MRC LMB

Title: Linking human neurodevelopmental timing and evolution

Abstract: Many hallmark features of the human brain, including its large size, complex neuronal architecture, and extensive connectivity, have emerged alongside a strikingly prolonged developmental timeline. In this talk, I will examine how extended neurodevelopmental time contributes to distinct human brain morphologies, using comparative human and mouse brain organoid models. I will present evidence for a newly identified evolutionary timing mechanism based on calcium dynamics, and discuss how this mechanism is linked to the expansion of axon tract morphologies in humans, a key feature underlying human brain connectivity.

TALK2 :

Name: James Fitzsimmons

Title: Brassinosteroid controls leaf air space patterning non-cell autonomously by promoting epidermal growth

Abstract: Plant leaves can be composed of up to 70% air in a network of intercellular spaces between mesophyll cells. Intercellular leaf air spaces are critical for gas exchange and enhance light scattering for photosynthesis, but little is known about how they form or develop. We tested a century old hypothesis that faster growth in the epidermis pulls the internal mesophyll cells apart to form air spaces. We characterise air space development in the first true leaves of A. thaliana and show that the phytohormone brassinosteroid is required for palisade mesophyll air space expansion. We demonstrate that epidermal brassinosteroid perception is sufficient to promote air space patterning in palisade mesophyll non-cell autonomously, and that an absence of brassinosteroid signalling leads to air spaces being lost during leaf development. We then tested whether restricting epidermal growth could reduce mesophyll air space. By expressing the growth repressing E3 ligase BIG BROTHER in the epidermis, we show that epidermal growth restriction reduces air space expansion in the neighbouring mesophyll cell layers. Overall, we propose that brassinosteroid signalling promotes epidermal growth to pattern air spaces in the palisade mesophyll.