The observations described here on gene expression in ET-743 and PM00104 resistant chondrosarcoma cell lines may provide the basis for such future studies. Rho small GTPases are a large family of highly conserved signalling proteins that contribute to biological processes as diverse as host-pathogen interactions, wound healing, development, and cancer. They play fundamental roles in eukaryotic cell division, cell morphogenesis and cell movement, through effects on actin and microtubule cytoskeletons, gene expression, and enzyme activity. The intracellular Dronedarone hydrochloride location of these proteins is important, and in plants the active forms of certain Rhos accumulate in patches that induce local cell outgrowths. Activation of the Rho-ofPlants proteins may occur by transcriptional up-regulation of ROP expression, or by the modulation of ROP activity via ROP-regulators that might themselves be transcriptionally or post-transcriptionally regulated. One of the best systems for studying ROP activity is the developing root hair cell. RH cells produce hairs that make up the majority of the root surface area of many crops and play an essential role in nutrient and water uptake from the soil, in anchorage, and in interactions with pathogens and symbionts. Development of RHs unfolds in a well-known sequence. RH cells are first Indaconitine formed at the root tip, and subsequently elongate while migrating away from the tip. In many plant species each RH cell has a single hair placed close to the basal end of the cell, an arrangement that leads to regular spacing of root hairs, and is thought to help maximise nutrient uptake. A typical wildtype root hair is shown in Figure 1A and an example of the accumulation of ROPs prior to hair growth in Figure 1B. Type I ROPs accumulate at predictable sites on the RH cell membrane where growth is about to take place, and RH growth is stimulated when ROP activity is experimentally increased. Root hair development is regulated by the plant hormone auxin. Auxin-mediated degradation of AUX/IAA proteins has been identified as affecting RH position, as well as many other aspects of root hair development including initiation, timing, and growth.