Search

Naturally occurring genetic variation for contents of cationic minerals in seeds of Arabidopsis thaliana was studied by screening a series of accessions (ecotypes) for Ca, Fe, K, Mg, Mn, Na, Zn, and for total contents of P. Variation was observed for all minerals and correlations between contents of various minerals were present, most noticeably between Ca and Mg, P and Mg, and P and Mn. The genetic basis of this variation was further studied by QTL analysis, using the Landsberg erecta (L er) × Cape Verde Islands (Cvi) recombinant inbred population. For all minerals, except Na, one or more QTL were detected, explaining up to 78% of the variation. The map positions of several QTL were confirmed by analysis of near isogenic lines, carrying small Cvi introgressions in L er background. Interesting co-locations of QTL suggest pleiotropic effects, due to physiological coupling of the accumulation of certain minerals or to linkage of different genes. By comparing the map positions of QTL with the positions of genes expected to play a role in cation translocation, several candidate genes are suggested. [ABSTRACT FROM AUTHOR]

The tomato (Solanum lycopersicum L.) slender mutant procera (pro) was analysed for its relationship with gibberellin (GA) by combining it with GA deficiency due to the gib-1 mutation. The sensitivity to GA biosynthesis inhibitors and the GA content were measured in the pro gib-1 double mutant. In the gib-1 mutant background, the pro mutation strongly reduced the GA requirement for seed germination and stem growth and almost fully restored the morphological leaf defects of the gib-1 mutant. An end-of-day far-red light treatment, when applied to the various genotypes, indicated that GAs are required for a response to this treatment, but that it act independently of the Pro gene product. [ABSTRACT FROM AUTHOR]

An inventory of genetic differences in flowering time in Arabidopsisis presented and discussed. Many genes influence the transition to flowering in a quantitative way. Two groups of mutants and natural variants can be distinguished: those that are responsive to environmental factors and those that are less responsive or unresponsive. it is possible that all late/early-flowering mutants isolated to date carry a mutation with an effect, either promotive or repressive, on a floral repressor. The interaction between light perception and flowering has been studied by analysis of phytochrome -- and cryptochrome deficient mutants, which showed that phyA and probably also cryptochrome have a promotive role in flowering, whereas phyB and other stable phytochromes have an inhibitory role. A circadian rhythm is important in establishing daylength sensitivity, as was shown by the phenotype of the elf3 mutants. [ABSTRACT FROM AUTHOR]

A dwarf mutant of Arabidopsis thaliana (L.) Heynh. was found to be less sensitive to applied gibberellins than the wild type, and this character was controlled by one partially-dominant gene (denoted Gai) located on chromosome 1. This mutant resembled gibberellin-deficient mutants since not only stem growth, but also apical dominance and seed germination were reduced. However, in contrast to the latter mutants, gibberellin does not reverse these effects in the Gai mutant. The insensitivity of the mutant could be quantified in much more detail in the recombinant of this mutation with the GA deficient mutant. ga-1/ga-1. Endogenous gibberellins of the Gai mutant did not differ from the wild type either in quantity or composition. The data suggest that the gene controls a step involved in gibberellin action. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) insensitive mutants of Arabidopsis thaliana (L.) Heynh. were isolated by selecting plants which grew well on medium containing 10μM ABA. From the progeny of approximately 3500 mutagen-treated seeds, five mutants of at least three different loci were isolated. Three mutants were characterized, moreover, by a reduced seed dormancy and by symptoms of withering, indicating disturbed water relations and, therefore, resembled phenotypically the ABA-deficient mutants we described earlier in this species. Two mutants showed in addition only a reduction of seed dormancy. Compared to wild type, all mutants showed similar or increased levels of endogenous ABA in developing seeds and fruits (siliquae). The role of the different genes involved in relation to the mechanism of ABA action. [ABSTRACT FROM AUTHOR]

The use of genetics in plant biology aims at the physiological and molecular genetical characterization of the phenotypic variation for the trait under study. Efficient mutant and gene isolation procedures have been developed for a number of plant models such as Arabidopsis thaliana. For this, the map position of the genes and insertion mutagenesis are used. The latter also allows the characterization of genes that are not easily recognized in mutant approaches, by using enhancer or gene-trapping procedures and reverse genetics. In addition to mutants, natural variation present among wild and cultivated varieties of a species provides an important source of genetic variation. The use of molecular markers, advanced mapping populations and specific cytogenetic stocks in case of polyploids, enables a detailed characterization of such natural variation even when it is of a quantitative and polygenic nature. Examples of the various genetic approaches are given. [ABSTRACT FROM AUTHOR]

Photomorphogenesis of tomato (Lycopersicon esculentum Mill.) is being studied with the aid of mutants which are modified either in their photoreceptor composition or in their signal transduction chain(s). Phytochrome chromophore mutants, presumably deficient in all phytochromes, and mutants specifically deficient in phytochrome A (phyA) or B1(phyB1) have been used to study the roles played by phytochromes in photomorphogenesis. In addition, other mutants, including transgenic lines overproducing phyA, exhibit exaggerated photomorphogenesis. Studies using these mutants are reviewed, with emphasis being placed on anthocyanin biosynthesis and plastid development as model systems for the dissection of the complex interactions between photoreceptors and to elucidate the nature of photoreceptor transduction chains. Recently, new mutants have been isolated by screening in a phyA,phyB1-deficient background. The novel phenotypes selected are candidates for mutants in additional photoreceptors or their transduction chains. [ABSTRACT FROM AUTHOR]

Siliqua development was studied in the wild type line Landsberg erecta and the GA‐sensitive mutant ga‐1 of Arabidopsis thaliana (L.) Heynh. Reciprocal crosses between wild type and ga‐l mutant, and self pollinations of either parent have shown that siliqua growth is determined by endogenous GAs originating from maternal tissues and embryo. The ga‐1 mutant either self pollinated or cross‐pollinated with wild type pollen showed reduced siliqua growth, which to a large extent could be overcome by exogenously applied GAs. The siliquae of the ga‐1 mutant possessed very reduced ent‐kaurene synthesizing capacity and no detectable endogenous GA‐activity indicating an early block in the GA‐biosynthetic pathway. Seed weight is not affected by GA‐deficiency during development. [ABSTRACT FROM AUTHOR]