Expression of carotenoid biosynthetic pathway genes and changes in carotenoids during ripening in tomato (Lycopersicon esculentum).

To study the expression pattern of carotenoid biosynthetic pathway genes, changes in their expression
at different stages of maturity in tomato fruit (cv. Arka Ahuti) were investigated. The genes regulating
carotenoid production were quantified by a dot blot method using a DIG (dioxigenin) labelling and
detection kit. The results revealed that there was an increase in the levels of upstream genes of the
carotenoid biosynthetic pathway such as 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR),
4-hydroxy-3-methyl-but-2-enyl diphosphate reductase (Lyt B), phytoene synthase (PSY), phytoene
desaturase (PDS) and z-carotene desaturase (ZDS) by 2–4 fold at the breaker stage as compared to leaf.
The lycopene and b-carotene content was analyzed by HPLC at different stages of maturity. The
lycopene (15.33 � 0.24 mg per 100 g) and b-carotene (10.37 � 0.46 mg per 100 g) content were found to
be highest at 5 days post-breaker and 10 days post-breaker stage, respectively. The lycopene
accumulation pattern also coincided with the color values at different stages of maturity. These studies
may provide insight into devising gene-based strategies for enhancing carotenoid accumulation in
tomato fruits.