Two SCARECROW-LIKE genes are induced in response to exogenous auxin in rooting-competent cuttings of distantly related forest species.

Abstract

This paper reports for the first time the identification of SCARECROW-LIKE genes from two distantly-related forest species, Pinus radiata and Castanea sativa, which are auxin-induced in rooting-competent cuttings before the activation of cell division that gives rise to adventitious root formation. The predicted protein sequences contain domains characteristic of the GRAS protein family, and show a strong similarity to the SCARECROW-LIKE proteins, which indicates conserved functions of these proteins. Quantitative RT-PCR analysis shows that these genes are expressed at relatively high levels in roots. In addition, an induction of the mRNA levels in rooting-competent cuttings from P. radiata and C. sativa in response to exogenous auxin is observed within the first 24 h of the root induction process, a time when cell reorganization takes place, prior to the resumption of cell division and to the appearance of adventitious root primordia. These results suggest that SCARECROW-LIKE genes may play a role at very early stages of adventitious root formation.