Repression of chilling-induced ACC accumulation in transgenic citrus by over-production of antisense 1-aminocyclopropane-1-carboxylate synthase RNA

A chilling-inducible ACC synthase gene (CS-ACS1 ) has recently been identified from Citrus sinensis. This CS-ACS1 gene was constructed in an inverted orientation and placed under the control of the double 35S promoter. The antisense CS-ACS1 transgene was introduced into Carrizo citrange, C. sinensis (L.) Osbeck and Poncirus trifoliate by Agrobacterium-mediated gene transfer. The transformation efficiency in the transformation of citrus stem segment was improved significantly to 87 and 88% for Poncirus trifoliate (L.) Raf and Carrizo citrange, respectively. The transgenic citrus lines that produce higher level of antisense ACS RNA were found to repress the increase of ACC content following the chilling treatment. This work represents the first example in controlling the ethylene biosynthesis in citrus plants through the genetic engineering approach.