Skip to main content
ARS Home » Research » Publications at this Location » Publication #92645
Title: TRANSFORMATION BY AGROBACTERIUM RHIZOGENES. ANNUAL FLOWERING IN TWO BIENNIALS, BELGIAN ENDIVE(CICHORIUM INTYBUS) AND CARROT (DACUS CARROTA)

Author
item LIMAMI, M - INRA, VERSAILLE, FRANCE
item SUN, LI-YAN - INRA, VERSAILLE, FRANCE
item DOUAT, CORINNE - INRA, VERSAILLE, FRANCE
item Helgeson, John
item TEPFER, DAVID - INRA, VERSAILLE, FRANCE

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bacteria of the Agrobacterium species, such as A. Rhizogenes or A. tumefacians insert DNA into the nucleus of the recipient plant, thereby providing new genes that are now expressed by the plant. Such plants are termed "transformed plants." In the case of Agrobacterium rhizogenes, the insertion of this DNA often results in heavy production of roots on the etransformed plants. However, in the study reported here the major effect was a change of the biennial (flowering every other year) to the annual (flowering each year) of the two different transformed species, endive and carrot. The change was retained in sexual progeny resulting from crosses of the transformed plants even though other traits of the transformed plants, such as heavy root formation and crinkled leaves were not retained. These results indicate that the change of a plant to an annual rather than a perennial characteristic can in some cases be mediated by soil bacteria. This finding has major evolutionary implication as it could be one mechanism whereby certain plants evolved from plants that flower every other year to those that flower every year. Also, such a change could greatly speed up the production of new varieties from these plants as now crosses could be done each year rather than every other year. Savings in time could then result in substantial savings in production costs for these important crops.

Technical Abstract: Genetic transformation of Belgian endive (Cichorium intybus) and carrot (Dacus carrota) by Agrobacterium rhizogenes resulted in a transformed phenotype, including annual flowering. Back-crossing of transformed (T1) endive plants produced a line that retained annual flowering in the absence of the other traits associated with A. rhizogenes transformation. Annualism was correlated with the segregation of a truncated T-DNA insertion. During vegetative growth, carbohydrate reserves accumulated normally in these annuals, and they were properly mobilized prior to anthesis. The effects of individual Ri TL-DNA genes on flowering were tested in carrot, where rolC was the primary promoter of annualism and rolD caused extreme dwarfism. We discuss the possible adaptive significance of this attenuation of the phenotypic effects of Ri TL-DNA.