Reversion of the negative selective effect of negative marker proteins as selection procedure

Method for preparing transformed plant cells or organisms. Method for preparing transformed plant cells or organisms comprises first transfecting a population of plant cells, already containing at least one marker protein (MP) that can exert a direct or indirect toxic effect, with at least one nucleic acid sequence (A) together with at least one compound (I) able to reduce expression, amount, activity and/or function of MP. Transfected cells that contain (A) in their genome and, because of the activity of (I) have a growth advantage relative to non-transformed cells are selected, under conditions where MP exerts its toxic effect on non-transformed cells. Independent claims are also included for the following: (1) plant-derived 5-methylthioribose kinase (MRTK) having any of 5 sequences (134-327 amino acids) reproduced; (2) nucleic acid (II) encoding MRTK and having any of 5 sequences (404-1011 nucleotides) reproduced; (3) double-stranded RNA (III) comprising a sense strand (ss) essentially identical with at least part of the sense transcript of nucleic acid that encodes MP and an antisense strand essentially, best completely, complementary with ss; (4) transgenic expression cassette (EC) containing: (a) a promoter (P) functional in plants and a sequence (IV) that encodes (III); or (b) a sequence encoding at least part of MP, linked to P in the antisense orientation; (5) transgenic vector containing EC; and (6) transgenic plant containing (III), EC or the vector of (5), also derived tissue, organs, parts, cells, cell cultures and reproductive material. Die vorliegende Erfindung betrifft Verfahren zur Herstellung transformierter pflanzlicher Zellen oder Organismen durch Transformation einer Population pflanzlicher Zellen, die mindestens ein Markerprotein mit einem für diese direkt oder indirekt toxischen Effekt umfasst, mit mindestens einer zu insertierenden Nukleinsäuresequenz in Kombination mit mindestens einer Verbindung - bevorzugt einem DNA-Konstrukt - befähigt zur Verminderung der Expression, Menge, Aktivität und/oder Funktion des Markerproteins, wobei die transformierten pflanzlichen Zellen infolge der Wirkung besagter Verbindung gegenüber nicht-transformierten Zellen einen Wachstumsvorteil haben.