Genetic and physiological characterization of tomato cv. Micro-Tom

Abstract

Based on its compact habit, Micro-Tom, a dwarf cultivar of tomato (Solanum lycopersicum L.), has been proposed as a preferred variety to carry out molecular research in tomato. This cultivar, however, is poorly characterized. It is shown here that Micro-Tom has mutations in the SELF-PRUNING (SP) and DWARF (D) genes. In addition to this, it is also shown that Micro-Tom harbours at least two independently segregating resistance loci to the plant pathogen Cladosporium fulvum. The presence of the self-pruning mutation in Micro-Tom, that generates a determinate phenotype, was confirmed by crossing and sequence analysis. It was also found that Micro-Tom has a mutation in the DWARF gene (d) that leads to mis-splicing and production of at least two shorter mRNAs. The d mutation is predicted to generate truncated DWARF protein. The d sequence defect co-segregates with dark-green and rugose leaves, characteristics of brassinosteroid biosynthesis mutants. Micro-Tom also carries at least another mutation producing internode length reduction that affects plant height but not active gibberellin (GA) levels, which were similar in dwarf and tall Micro-TomxSeverianin segregants. GAs and brassinosteroids act synergistically in Micro-Tom, and the response to GA depends on brassinosteroids because the elongation of internodes was at least six times higher when GA(3) was applied simultaneously with brassinolide. A novel variety, Micro-0 that is fully susceptible to C. fulvum and almost as dwarf as Micro-Tom, has been generated from the cross of Cf0xMicro-Tom. This line represents a valuable resource for future analysis of Cf resistance genes through breeding or transformation.

Reduced arbuscular mycorrhizal colonization in tomato ethylene mutants

“…However, different from other tomato BR mutants, such as dumpy and curl-3 (Koka et al, 2000), the dwarf allele harbored by MT does not result in a drastic phenotype, but produces a miniaturized plant with a proportional reduction in all organs size (Meissner et al, 1997). At least another unknown mutation is responsible for MT reduced size (Lima et al, 2004), although it has been demonstrated that this cultivar is not GA deficient/insensitive (Marti et al, 2006).…”

“…This procedure was repeated until BC3F2. One of the mutations contributing to MT small size is dwarf (Lima et al, 2004;Marti et al, 2006), which leads to a reduction in brassinosteroid (BR) levels (Bishop et al, 1999). However, different from other tomato BR mutants, such as dumpy and curl-3 (Koka et al, 2000), the dwarf allele harbored by MT does not result in a drastic phenotype, but produces a miniaturized plant with a proportional reduction in all organs size (Meissner et al, 1997).…”

The Tomato FRUITFULL Homologs TDR4/FUL1 and MBP7/FUL2 Regulate Ethylene-Independent Aspects of Fruit Ripening

“…However, MT plants harbor four independent mutations, including one in the brassinosteroid pathway (Martí et al, 2006), which may influence tomato development and ripening. For example, the size of MT fruits is quite variable, and silencing of TAGL1 did not lead to reduced pericarp thickness in MT, but showed this phenotype only in the nondwarf variety Ailsa Craig (Itkin et al, 2009;Vrebalov et al, 2009).…”

Características fisiológicas de microtomateiros fitocromo-mutantes

“…P. 3037 -37200-000 -Lavras, MG -silviojramos@gmail.com.br (Lycopersicon esculentum cv Micro-Tom) foi proposta por Meissner et al (1997) como um modelo genético, que produz frutos e sementes viáveis, e podem ser cultivadas em vasos de 50-150 mL de substrato, completando seu ciclo de vida entre 70-90 dias, superando assim as desvantagens do cultivo de tomateiro em relação a A. thaliana, para fins de pesquisa. Atualmente Micro-Tom (MT) tem sido proposta como a cultivar preferencial para pesquisas a nível molecular em tomateiro (MARTÍ et al, 2006).…”

“…Aspectos morfológicos e genéticos têm sido estudados em microtomateiros (MARTÍ et al, 2006;MEISSNER et al, 1997) e naqueles fitocromo-mutantes, o potencial de regeneração in vitro (CARVALHO, 2003). Diversos aspectos fisiológicos ainda não foram caracterizados, inclusive em mutantes de porte normal, os quais são fundamentais para o entendimento dos complexos efeitos da radiação sobre processos do desenvolvimento dependentes de fitocromo.…”