Genetic characterization of the polycotyledon locus in tomato

Abstract

Developmental mutants serve as a useful material to unravel the mechanisms necessary for organ development. The polycotyledon (poc) mutant of tomato, with multiple cotyledons in the seedling and varied phenotypic effects in the adult plant is one such mutant. Studies using physiological and anatomical methods in our lab suggest that POC is involved in the negative regulation of polar auxin transport, which is likely the reason for the pleiotropic phenotype in the mutant. Because of the physiological significance of the polycotyledon mutant described in this paper and also being first of its kind in tomato and also other plant species, we are using a map-based cloning approach to map the polycotyledon gene. Molecular mapping of this locus using segregating interspecific F2 mapping population localized polycotyledon gene close to TG424 marker on the long arm of chromosome 9. The closest marker mapped was a PCR marker identified in this study, E8A2 at a distance of 7.4 cM from the poc locus. The absence of tightly linked RAPD markers and the non-availability of more mapped markers in this region led us to initiate chromosome walk to polycotyledon gene. Both the flanking markers TG248 and E8A2 were used to screen the BAC library and a contig was developed for TG248 marker. The BAC-end sequences were analyzed for their use as RFLP markers to enrich this region for markers. Analysis of the BAC-end sequences revealed that poc is localized in the region surrounded by copia-like retrotransposon elements explaining the absence of markers in the euchromatin region on long arm of chromosome 9. Further studies identified two BAC-end sequences which mapped around the poc locus and also indicated very low physical versus genetic distance ratio in this region. The double mutant analyses of poc with the other two known polycotyledon mutants of tomato, pct and dem revealed allelism with pct; therefore, the poc mutant was named as pct1-2, and also the original pct mutant was renamed as pct1-1.

The root as a drill

“…The application of 1-MCP also reduced the polar auxin transport in tomato roots, suggesting that the auxin-ethylene interaction may be partly mediated by modulation of polar auxin transport. Consistent with this view, the pct1-2 mutant that has a nearly 3-fold higher auxin transport than wild type, 63,64 displayed a close to normal root penetration in the Soilrite in presence of 1-MCP. However, the application of a polar auxin transport inhibitor, TIBA, which interferes with the vesicle trafficking of auxin transporters, 65 along with 1-MCP partially inhibited the root penetration of the pct1-2 mutant.…”

Tomato Root Penetration in Soil Requires a Coaction between Ethylene and Auxin Signaling

“…Root elongation growth is also modulated by the accumulation of auxin at the root tip (Petersson et al, 2009), and the accumulation of auxin above a threshold level inhibits root elongation. In accordance with this, seedlings of the enhanced polar auxin transport mutant of tomato (Solanum lycopersicum), polycotyledon (pct1-2), have shorter roots, and inhibition of auxin transport in the mutant stimulates root elongation (Al-Hammadi et al, 2003;Madishetty et al, 2006).…”

“…Wild-type tomato (Solanum lycopersicum), Nr mutant, and pct1-2 mutant (Madishetty et al, 2006) seeds, all in the Ailsa Craig background, were used in this study. The pct1-2 mutant was crossed with a DR5::GUS transgenic line , and homozygous pct1-2 seedlings with GUS activity in the F4 generation were used.…”

Sexual Propagation of the Tunisian Spinescent Opuntia ficus-indica (L.) Mill., Morphogenetic Deployment and Polymorphism

“…In fact, many species of the Cactaceae have prolonged seed dormancy with low or null germination (Rojas-Aréchiga and Vázquez-Yañes, 2000). Abnormalities and polyembryony were previously reported by authors (Gates, 1910;Went, 1944;Haskell, 1954;Harrison, 1964;Dessureaux, 1967;Kerr, 1985;Rajora and Zsuffa, 1986;Pimienta-Barrios, 1990;Asker and Jerling, 1992;Perez, 1993;Mondragon and Pimienta-Barrios, 1995;Garcia and PimientaBarrios, 1996;Nieddu and Chessa, 1996;Vélez-Gutiérrez and Rodríguez-Garay, 1996;Conway and Poethig, 1997;NegronOrtiz, 1998;Vernon et al, 2001;Mondragon, 2001;Graz, 2001;Azumi et al, 2002;Nagesh and Kardam, 2004;Khan 2006;Madishetty et al, 2006;Korekar et al, 2012;Narantsetseg, 2014;Shveta and Veenu, 2015) and tracking the evolution of the obtained seedlings allows the report of those phenomenons in our study. On the other hand, among the main modifications in the course of the development of O. ficus-indica were the modified stems (cladodes) which have undergone changes towards succulency, anatomy and physiology (Sudzuki Hills, 1995).…”

“…Researchers have documented this phenomenon of tricotyledonous mutant in many plant species (Holtorp, 1944;Reynard, 1952;Kerr, 1985;Nagesh and Kardam, 2004;Madishetty et al, 2006). More generally, the production of an abnormal number of cotyledons has been referred to as pleiocotyly (Korekar et al, 2012).…”