Isolation of biochemical mutants using haploid mesophyll protosplasts of Hyoscyamus muticus : IV. Biochemical characterisation of nitrate non-utilizing clones

Species with Haploid or Doubled Haploid Protocols

In this chapter, we present a list of species (and few interspecific hybrids) where haploids and/or doubled haploids have been published, including the method by which they were obtained and the corresponding references. This list is an update of the compilation work of Maluszynski et al. published in 2003, including new species for which protocols were not available at that time, and also novel methodologies developed during these years. The list includes 383 different backgrounds. In this book, we present full protocols to produce DHs in 43 of the species included in this list. In addition, this book includes a chapter for one species not included in the list. This makes a total of 384 species where haploids and/or DHs have been reported up to date.

Involvement of chlA, E, M, and N loci in Escherichia coli molybdopterin biosynthesis

All molybdenum enzymes except nitrogenase contain a common molybdenum cofactor, whose organic moiety is a novel pterin called molybdopterin (MPT). To assist in elucidating the biosynthetic pathway of MPT, two MPT-deficient mutants of Escherichia coli K-12 were isolated. They lacked activities of the molybdenum enzymes nitrate reductase and formate dehydrogenase, did not reconstitute apo nitrate reductase from a Neurospora crassa nit-1 strain, and did not yield form A, a derivative of MPT. By P1 mapping, these two mutations mapped to chlA and chlE, loci previously postulated but never definitely shown to be involved in MPT biosynthesis. The two new mutations are in different genetic complementation groups from previously isolated chlA and chlE mutations and have been designated as chlM and chlN (closely linked to chlA and chlE, respectively). The reported presence of Mo cofactor activity in the chlA1 strain is shown to be due to in vitro synthesis of MPT through complementation between a trypsin-sensitive macromolecule from the chlA1 strain and a low-molecular-weight compound from the nit-l strain.

Repair in vitro of nitrate reductase-deficient tobacco mutants (cnxA) by molybdate and by molybdenum cofactor

Two nitrate reductase-deficient mutant cell lines (CnxA68/2, CnxA101) of Nicotiana tabacum are shown to be repairable under in-vitro conditions by (i) molybdate or (ii) by preparations of active molybdenum cofactor of homologous or heterologous origin, thereby yielding about 20% and 80%, respectively, of the corresponding wild-type NADH-nitrate reductase (EC 1.6.6.1) activity. In-vitro repair of nitrate reductase activity is dependent on sulphydryl-group protecting reagents and ethylenediaminetetraacetic acid (EDTA) in the extraction medium, the nitrogen source in the growth medium and the age of the cells. The results support the conclusion that the cnxA gene controls the insertion of molybdenum into the molybdenum cofactor. They are consistent with the idea of two interlinked pathways for the metabolic processing of molybdenum acquisition, one involving the synthesis of the structural moiety of the molybdenum cofactor and the other involving processing of the molybdate anion.