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

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

IDENTIFICATION OF GENES INVOLVED IN THE PROCESS OF MYCORRHIZA FORMATION IN POPULUS ALBA X TUBER BORCHII

PAOLOCCI F., PORCEDDU A., RUBINI A., RICCIONI C., TOPINI F., ARCIONI S.

Istituto di Ricerche sul Miglioramento Genetico delle Piante Foraggere del CNR, Via Madonna Alta 130, Perugia

F.Paolocci@irmgpf.pg.cnr.it

ectomycorrhizae, differential display, truffle

The process of mycorrhiza formation can be divided in several phases I) cross-talk between symbiotic partners II) enhanced and polarized growth III) physical interaction between fungus and plant IV) formation of a three component structure: a mantle of fungal tissue which envelopes the root, a labyrinthine inward growth of hyphae between the epidermis and cortical cells, an outwardy growing system of hyphal elements. Little information is to date available on the genetic regulation of these phases. With the aim of identifying fungal genes involved in symbiotic partners cross talk a study of differential gene expression was initiated. The experimental design can be summarized as follows. Rooted plants of Populus alba and micelia of Tuber borchi were co-cultivated in vitro; after four weeks, when the growth rate difference between co-cultivated and control micelia was evident, RNAs were extracted and retrotranscribed to cDNA. Cloning of differentially expressed cDNAs was obtained via suppressive subtractive hybridization and cDNA-AFLP. Of the 150 clones analyzed 30 were 2,5 times more induced in the co-cultivated micelia than in the control one. Among these a prevalence of plasma membrane ATPases and genes involved in general metabolism such as nitrate permease, nitrate and nitrite reductase, was obseved. A gene encoding for 3'-phosphoadenosine-5'phosphosulfate (PAPS) reductase was the highest induced. As these finding pictured only fungus metabolism enhancement, it was questioned whether this result was a consequence of fungus plant cross talk or an unspecific metabolic response to root secretions. Gene expression analysis of micelia co-cultivated with several non-host plants are expected to provide informations about the specificity of gene induction. The cDNAs responsive only to the presence of the host plant will be suitable as molecular markers of early phases of the mycorrhization process.