Quick identification of the members of the glutamine synthetase gene family from sunflower by simultaneous amplification of cDNA with degenerate primers

A single degenerate glutamine synthetase (GS)-specific primer was used to a mplify the 3' end of cDNAs derived from different GS genes that are express ed in leaves and roots of sunflower (Helianthus annuus L. cv. Peredovic). F our types of GS cDNA (I, II, III and IV) were simultaneously amplified from leaves and five types (I, II, V, VI, VII) from roots with a minimum invest ment of time and experimental work, cDNAs II, III and IV encode chloroplast ic isoforms as deduced by the presence of chloroplastic GS-specific feature s in their sequences. The rest of cDNAs codifies cytosolic isoforms. Using cDNA-specific probes and primers, homologous sequences to all GS cDNAs ampl ified from cv. Peredovic, except to cDNAs III and IV, were detected in the inbred line R41. This result strongly suggests that the three cDNAs for chl oroplastic isoform are allelic sequences from the same locus, and since cDN A type IV contains sequences derived from cDNAs II and III, it indicates a recombinational origin. The results presented are consistent with the exist ence of a GS gene family in sunflower with at least five members. Four of t hem, named ggs1.1 to ggs1.4, codify for the cytosolic isoforms (cDNAs I, V, VI and VII). A fifth member, named ggs2, from which three allelic sequence s (cDNAs II, III and IV) have been cloned, encodes the chloroplastic isofor m.