Sex-specific marker and trans-zeatin ribosidase in female annual Mercury

Mercurialis annua is dioecious with unisexual flowers lacking vestiges of opposite sex organs. Previously, we showed that the cytokinin trans-zeatin (t-Z) was correlated with female sex genes whereas t-Z production stops at its precursor, the trans-zeatin riboside (t-ZR) in males. Hoping to further relate sex genes and t-Z production, we underwent a search for eventual female-specific DNA and for a specific enzyme producing the feminizing signal. We report the cloning of a female-specific fragment and the identification of a t-ZR beta-ribosidase. The specific-DNA was isolated by AP-PCR (arbitrary primed-polymerase chain reaction) from a female line. Its sequence shows significant identity with the precursor of the beta-subunit of polygalacturonase (PG) isoenzymel cDNA expressed during tomato fruit development. A stereospecific t-ZR beta-ribosidase activity was purified 490-fold from female apices. It belongs to a female non-covalent enzymatic complex which contains a fructose 1-6 biphosphate aldolase and two 14-3-3 proteins (N-terminal sequences). Furthermore, a cytokinin-oxidase(s) and a PG activity were associated to the purified complex. Together, these results suggest that one PG subunit could be the product of the female-specific DNA which, consequently, cannot be a feminizing allele. Complete purification of the t-ZR ribosidase will enable us to further investigate female sex genes and female-marker relationships. (C) 1998 Published by Elsevier Science Ireland Ltd.