The Mutated Gene Responsible for Agravitropic Growth of the Weeping Morning Glory, Shidare-asagao

Abstract

An agravitropic mutant of morning glory (Pharbitis nil), weeping, has defect in shoot gravitropism. Our previous results showed that weeping were also defective in endodermis development and in shoot circumnutation. Such defects in circumnutation were also observed in endodermis-less Arabidopsis mutant, scarecrow (scr). In search of the mutated gene of weeping, cDNAs for SCR homolog from morning glory (PnSCR) were cloned from both wild type and weeping. We found an amino acid insertion in PnSCR obtained from weeping. To investigate whether this insertion inactivates the PnSCR functions, we performed complementation test by introducing either wild type PnSCR or weeping type PnSCR, respectively, to Arabidopsis scarecrow mutants. As a result, none of the defects were rescued by weeping type PnSCR, whereas wild type PnSCR rescued them. This result indicates that defects in gravitropism, endodermis development, and circumnutation observed in weeping are attributable to the loss of function of PnSCR.