Dr. K. (Kaisa) Kajala

Hugo R. Kruytgebouw
Padualaan 8
Kamer Z306
3584 CH Utrecht

Dr. K. (Kaisa) Kajala

Associate Professor
Plant-Environment Signaling
+31 30 253 6871

My main research interest is understanding how different plant cell types have evolved, and how these cell types develop, respond to environmental changes and contribute to plant fitness. My research is carried out in both model and crop species, including Arabidopsis, tomato, rice, and legumes.



Plants are the primary source of energy for humankind, and they do an incredible job growing come rain or shine. As they are rooted to the ground and unable to escape the challenges they face, they have evolved a remarkable capacity to modulate their growth and development in response to the environment. This phenotypic plasticity is controlled by tightly regulated changes to gene expression. Understanding the molecular mechanisms of how different plant tissues and plant cell types respond to environmental challenges, such as drought, flooding and light, will allow us to tap into uncharted potential for breeding smarter and more resilient crops. Research projects ongoing in my lab include the following:


Exodermis of tomato root has lignified Casparian strip and suberin lamellaDynamic root barriers: Exodermis

Exodermis is a root cell type located just under the epidermis, the outermost skin of the root, and it protects the root from drying and drowning. The water- and air-proofing capabilities of exodermis are brought about by two hydrophobic additions to the cell walls: 1) a localized lignin band called Casparian strip that divides the layer to two polarities, inside and outside, and 2) suberin lamellae deposited all around the exodermal cells.

These barriers protect the root in various ways. In drought, the exodermis allows the plants to have higher water retention in drought conditions, making them more drought-tolerant. In flooding, the exodermis prevents oxygen loss from the roots into the soil, leading to more oxygen for root respiration and better flooding tolerance. In saline soils, the exodermis allows increased control of ion and salt uptake from the soil, enhancing salinity tolerance.

Not all plants have exodermis, but all vascular plants have a cell layer called endodermis. Endodermis has both the Casparian strip and the suberin lamella, and the development of endodermis has been elucidated well on the molecular level in the model plant Arabidopsis thaliana that happens to lack the exodermis. The endodermis appears evolutionarily more ancient, but the evolutionary origins of exodermis have yet to be elucidated. Did exodermis evolve once, or independently in different lineages? Did exodermis evolve by co-opting modules of endodermal development modules to a new cell layer? What regulates these modules in exodermis? How are the environmental cues integrated with the exodermal development? These are some of the questions that I hope to answer.

Funding sources: Marie Sklodowska Curie Actions fellowship (2018-2021), NWO-VIDI (2021-2026) 

Team members: Leonardo Jo, Rianne Kluck, Mariana Silva Artur (now at WUR)


Plant neighbour detection: light

Plants can sense shade and their neighbours through far-red light. For crop species, such as tomato, shade affects resource allocation and very importantly, yield. The overall growth responses to shade, such as stem elongation and suppression of branching, are well known. However, the cellular development responses are not well characterized. I’m intrested in exploring the changes to the cellular morphology and anatomy in stems and roots in response to shade. Then, using cell type-specific tools we can explore the molecular mechanisms that link shade to changes to plant development. 

Funding sources: China Scholarship Council

Team members: Linge Li


Plant neighbour detection: touch

The first neighbor-detection cue in model species Arabidopsis is a touch cue on the leaf tip, triggered by surrounding leaf tips. The touch cue induces upward leaf movement, which in turn increases leaf-reflected far-red light in the canopy and triggers yield-reducing competitive growth between the plants. While it is well characterized how plants sense and respond to the leaf-reflected far-red light, the molecular basis of touch-induced leaf movement is unknown. We study the molecular basis of touch-induced leaf movement, and how different leaf blade and petiole cell types contribute to detection of touch, transmitting the signal and responding. Our preliminary data show that touch-induced leaf movement has a different genetic basis than light-mediated leaf movement, indicating the existence of a novel signaling pathway.


Funding source: NWO ALW Open Programme (2019 - 2022)

Team members: Chrysa Pantazopoulou





My previous research

Example of cell type-specific TRAP and INTACT lines

I carried out postdoctoral work at the Brady lab at University of California, Davis, where I generated an atlas of tomato root gene expression as part of the Integrative Plasticity project. The tomato atlas encompasses combinations of a dozen root cell and tissue types, multiple levels of regulation (chromatin accessibility, nuclear transcriptome, translatome) and different growth conditions (e.g. drought, flooding, plate, soil) for a domesticated tomato Solanum lycopesicum as well as a wild drought-tolerant relative Solanum pennellii.

Combining the functional genomics data with stress-responsive cell development phenotypes sheds light onto molecular mechanisms underlying the plasticity of development on cellular level. For example, we have found changes to the cortex anatomy in response to flooding and changes to exodermal development in response to drought in tomato.


Cross section of C4 leaf

My PhD research was in the Hibberd lab at University of Cambridge. I investigated the transcriptomes of C4 leaves as well as evolution of the elements that directed cell type-specific gene expression in mesophyll cells in the leaves of C4 plant Cleome gynandra.