Tetraspanins (TETs) are small transmembrane proteins that have emerged in animals as key players in numerous cellular processes including cell adhesion and fusion, intracellular membrane trafficking and signaling. The function of TET proteins is linked to their ability to laterally associate with each other and to engage in a wide range of specific molecular interactions with signaling proteins as well as lipids. These interactions result in the formation of a distinct class of membrane domains, the tetraspanin-enriched microdomains (TEMs) which function as dynamic, mobile signaling hubs within membranes that are important for proper cell function. As there is little known about TET functions in plants, we set out to study the developmental and cellular role of TETs in Arabidopsis.
Choline transporter like proteins in plants
Choline serves as a precursor for the synthesis of major membrane phospholipids, betaine and the neurotransmitter acetylcholine. Consequently, severe developmental defects and neurological disorders have been implicated with the interference of choline uptake, transport or metabolism. Choline transport is mediated by different transporter systems including the choline transporter like proteins (CTLs). Recently, we have isolated a novel member of the CTL family in Arabidopsis (AtCTL1/CHER1) that is involved in the elaboration of sieve pores and plates of phloem cells. Besides AtCTL1/CHER1, six other CTL are expressed in the Arabidopsis genome but nothing is known about their function. Therefore we started to investigate the physiological function of individual CTLs as well as their role and regulation during plant development and plant growth.