Plant physiologyJun 14, 2003

Increasing a natural pigment-producing gene in seeds delays germination and raises levels of plant pigments and growth hormone in Arabidopsis

Updated Feb 26, 2026

Abstract

Transgenic Arabidopsis seeds exhibited a 43-fold average increase in beta-carotene compared to controls.

Darker seeds were produced by transgenic plants overexpressing phytoene synthase.
Average beta-carotene content reached approximately 260 micrograms per gram of fresh weight.
Significant increases in other carotenoids, including lutein, violaxanthin, and chlorophyll, were observed.
Lycopene and alpha-carotene were produced in substantial amounts in transgenic seeds, while control plants had only trace levels.
Transgenic seeds showed delayed germination, correlated with increased carotenoid levels.
Abscisic acid levels increased alongside carotenoid accumulation, with the highest carotenoid levels corresponding to the highest abscisic acid content.

Simplified

Phytoene synthase catalyzes the dimerization of two molecules of geranylgeranyl pyrophosphate to phytoene and has been shown to be rate limiting for the synthesis of carotenoids. To elucidate if the capacity to produce phytoene is limiting also in the seed of Arabidopsis (Wassilewskija), a gene coding for an endogenous phytoene synthase was cloned and coupled to a seed-specific promoter, and the effects of the overexpression were examined. The resulting transgenic plants produced darker seeds, and extracts from the seed of five overexpressing plants had a 43-fold average increase of beta-carotene and a total average amount of beta-carotene of approximately 260 microg g-1 fresh weight. Lutein, violaxanthin, and chlorophyll were significantly increased, whereas the levels of zeaxanthin only increased by a factor 1.1. In addition, substantial levels of lycopene and alpha-carotene were produced in the seeds, whereas only trace amounts were found in the control plants. Seeds from the transgenic plants exhibited delayed germination, and the degree of delay was positively correlated with the increased levels of carotenoids. The abscisic acid levels followed the increase of the carotenoids, and plants having the highest carotenoid levels also had the highest abscisic acid content. Addition of gibberellic acid to the growth medium only partly restored germination of the transgenic seeds.

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