TETRASPANINs in Plants

Abstract

Tetraspanins are small transmembrane proteins that laterally associate with each other and cluster with numerous partner proteins as well as lipids. These interactions result in the formation of a distinct class of membrane domains, the tetraspanin-enriched microdomains (TEMs), which influence numerous cellular processes such as cell adhesion and fusion, intracellular membrane trafficking, signaling, morphogenesis, motility as well as interaction with pathogens and cancer development. The majority of information available about tetraspanins is based on studies using animal models or cell lines, but tetraspanins are also present in fungi and plants. Recent studies indicate that tetraspanins have important functions in plant development, reproduction and stress responses. Here we provide a brief summary of the current state of tetraspanin research in plants.

Keywords: Arabidopsis; embryogenesis; plant growth; plant reproduction; rice; tetraspanins.

Figure 1

Tetraspanin structure and expression patterns in A. thaliana. (A) A schematic representation of tetraspanin structure and membrane topology. Tetraspanins are composed of a small extracellular loop, a large extracellular loop (LEL), an intracellular loop, a N-terminal tail and a C-terminal tail. Red and yellow shading indicate the variable and conserved domains of the LEL, respectively. (B) Tetraspanin expression in reproductive A. thaliana cells and tissues. Pollen grains adhere to papilla on the stigmatic surface of the pistil, where they hydrate and subsequently germinate. Pollen tubes emerging from pollen grains grow through the transmitting tract toward the ovules, where they release their sperm cells to initiate fertilization. A germinating pollen tube representing the male gametophyte (vn, vegetative nucleus; sc sperm cells) and an ovule containing the embry sac, which represents the female gametophyte, (ac, antipodal cells; cc, central cell; ch, chalazal region of the ovule; ec, egg cell; f, funiculus; mp, micropyle; sy, synergid cells) are drawn at higher magnification. AtTETs expression pattern in different reproductive organs or structures as well as the subcellular localization of AtTETs in pollen tubes is indicated in red. (C) Tetraspanin expression pattern during A. thaliana embryo development. Embryos at different developmental stages are shown: globular, heart and torpedo stadium. Apical, central and basal domains are represented due to different patterns. Shoot (SAM) and root (RAM) apical meristems are indicated. AtTETs expression in different tissues of globular and heart shaped embryos is shown in red.