Tackling Companion Cell Identity

Phloem is in charge of transporting photosynthates and signalling molecules from source organs to non-photosynthetic tissues, like roots. For this purpose, the sieve element (SE) cells eliminate many organelles becoming a pipe specialized in transport that is physiologically dependent on neighbouring companion cells (CCs). Even if we know many genes important for SE specification and differentiation, little is known about the transcriptional programs governing companion cell identity and differentiation.

Using fluorescent cell markers expressed early during CC development in the root of Arabidopsis thaliana, we have identified a list of transcription factors and other proteins whose expression is enriched in CCs. To study the biology behind these candidates we are generating fluorescent marker lines, overexpressor lines and mutants.

Here we present novel factors that are expressed in CCs and might be involved in CC development. With our studies we will generate regulatory networks to help us understand better the identity of CCs and its relationship with the neighbouring SE.