Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.35

AN INTEGRATED APPROACH FOR THE STUDY OF SEXUAL DIFFERENTIATION OF CANNABIS SATIVA L.

V.M.C. MOLITERNI*, L. CATTIVELLI**, G. MANDOLINO*, P. RANALLI*

*) Istituto Sperimentale per le Colture Industriali, Via di Corticella 133, 40128 Bologna

**) Istituto Sperimentale per la Cerealicoltura, strada S. Protaso 302, 29017 Fiorenzuola d’Arda (PC)

Cannabis sativa, dioecy, sexual differentiation, sex linked markers, cDNA AFLP

Cannabis sativa is a dioecious species with unisexual flowers and sexual dimorphism occurring in a late stage of plant development only. Sex is determined by heteromorphic chromosomes (X and Y): male is the heterogametic sex (2n = 18+XY) and female is the homogametic one (2n = 18+XX). Despite of its chromosomal determination, the sexual phenotype of Cannabis often shows some flexibility. Anomalies in fact may occur in floral development, leading to the differentiation of hermaphrodite flowers or bisexual inflorescences (monoecious phenotype). For some genotypes it is also possible the complete sexual reversion by treatment with activators or inhibitors of the ethylene biosynthetic pathway.

The microscopic analysis of male and female apices at different stages of development, revealed that the earliest step in their sexual differentiation occurs as the leaves of the fourth node emerge. The genetic expression of male and female apices at this stage has been compared by cDNA AFLP. In order to discriminate the two sexes before sampling, a rapid method for sex determination has been developed, based on the PCR amplification of a 391 bp long, male-specific SCAR marker, directly from a leaf tissue fragment.

Seven of the several cDNA AFLP polymorphic fragments, have been identified to be differentially expressed in males and females apices at the fourth node; cloning and sequencing of the sub-clones, revealed that they belong to nine different mRNAs that were all induced in the female apices at this stage. The results of BLAST analysis for this clones led to the identification of their putative coding function and to their possible roles in this earliest step of sexual differentiation. Four of the induced clones belong respectively to the mRNA for a putative permease, for a putative kinesin, an SMT3 like protein and a RAC-GTP binding protein like .

The induction of these clones in female apices at this stage may suggest that they are involved in the early phase of the female sex differentiation; on the other hand, their under-expression in male apices could be correlated to the repression of female characteristics at this precocious stage of male apex sexual differentiation.