Auxin conjugate mutants

The formation of IAA conjugates is widely believed to be a means for removal of excess IAA produced during certain times of plant development and also in mutant plants where indolic precursors and IAA metabolites accumulate.32 In all higher and many lower plants, applied IAA is rapidly conjugated to form IAA—aspartate.33 The ability of plant tissues to make aspartate conjugates of a variety of active auxins is induced by pretreatment with auxin,34 and this induction was shown to be blocked by inhibitors of RNA and protein synthesis. After almost 50 years of study, an in vitro system from plants was described that accounts for the formation of IAA amide conjugates35 via a mechanism where the acidic auxin is adenylated followed by acyl transfer to the amino acid. The gene for this reaction had been discovered almost 20 years before, when GH3 from soybean was shown... 

Useful progress has been made in the genetics of GAs, ABA and, more recently, ethylene [11]. However, relatively few mutations have been reported involving auxins or cytokinins. Both recessive and dominant mutants have been isolated with increased resistance to synthetic auxins [8, 14, 16], and two mutants have been described with significantly altered levels of lAA or lAA conjugates [20, 22]. Mutations have been reported that affect the cytokinin requirement of tobacco leaf cells in culture [15], and cytokinin resistance and production in the moss Phys-comitrella patens [23]. 

---