Do we have the auxin receptor yet?

Several auxin‐binding proteins (ABP) have now been identified using a variety of techniques. A 43‐kDa glycoprotein thought to be a dimer of 22‐kDa subunits has been identified as a strong candidate for the auxin receptor that mediates cell elongation in etiolated maize shoots. The primary sequence has been deduced and several interesting structural features have been discerned. There is indirect evidence that this 22‐kDa ABP has a receptor function, the most compelling being that antibodies directed against the ABP can block an auxin‐induced response. There is evidence that changes in auxin‐induced growth capacity in shoots correlates with changes in the abundance of the 22‐kDa ABP suggesting that in some cases the 22‐kDa ABP may be limiting growth. Confirmation of receptor function for one of these newly‐identified ABP's should open the way for genetic manipulation of crop growth.