Pleiotropic morphological and abiotic stress resistance phenotypes of the hyper-abscisic acid producing Abo⁻ mutant in the periwinkle Catharanthus roseus

Abstract

The pleiotropic properties of aabo abo (Abo⁻) γ-ray induced mutant ofCatharanthus roseuscv. Nirmal, selected among the M₂ generation seeds for ability to germinate at 45°C, are described. The mutant produced seeds possessing tricotyledonous embryos, unlike the typically dicotyledonous embryos present in the wild type Abo⁺ seeds. In comparison to Abo⁺ adults, the mutant plants had short stature and lanceolate leaves. The vascular bundles in the leaves and stem were poorly developed. Leaf surfaces were highly trichomatous, epidermal, cortex and mesophyll cells were small sized and a large majority of stomata were closed. Besides high temperature, the mutant was salinity and water-stress tolerant. The abscisic acid (ABA) content in the leaves was about 500-fold higher. The genetic lesionabo responsible for the above pleiotropy was recessive and inherited in Mendelian fashion. The seedlings and adult plants of the mutant accumulated higher proline than Abo⁺ plants. The phenotypes ofabo abo mutants permitted the conclusions that (i) the mutant synthesizes ABA constitutively, (ii) both ABA-dependent and ABA independent pathways for proline and betaine accumulation are functional in the mutant, and (iii) cell division, elongation and differentiation processes in embryo and adult plant stages are affected in the mutant.