Transcript expression level analysis of phytoene synthase and phytoene desaturase associated with β-carotene content in selected Kenyan Bitter melon.

Background: Bitter melon (Momordica charantia L.) is a widely cultivated food and medicinal plant native to the world's subtropics and tropics. Constraints affecting cultivation of Bitter melon affect productivity of β-carotene. Knowing the mechanism that controls the transcription of the β-carotene biosynthesis genes in Bitter melon will be of great value in improving the yield of this important metabolite. Methods and Results: The expressions of β-carotene biosynthetic genes such as Phytoene Desaturase (PDS) and Phytoene Synthase (PSY) were evaluated in Bitter melon accessions 'GBK027049', 'NS1026', 'Mahy-ventura', '453B' and 'Sibuka532'. Transcript expression level analysis of PSY and PDS, and amount of β-carotene in leaf, stem, and fruit, were determined using quantitative polymerase chain reaction and high-performance liquid chromatography (HPLC). Root transcript expression was used as a negative control for determining relative fold change in other tissues. Expression of PSY in fruit (6 to 27-fold compared to the control) was higher than in the other organs for all accessions. This was also the case of PDS expression (10 to 29-fold compared to the control). Leaves had the highest β-carotene concentration (17.92–45.35 µg∙g⁻¹); there was no difference between stems (5.67–12.75 µg∙g⁻¹) and fruit (6.18–12.53 µg∙g⁻¹). The highest β-carotene content was in accessions 'GBK027049' (12.53–45.35 µg∙g⁻¹) and '453B' (6.18–32.09 µg∙g⁻¹). The PSY and PDS expressions were positively correlated with amount of β-carotene in leaves, stems, and fruits. Conclusion: Bitter melon leaves, especially those of 'GBK027049' and '453B' accessions, are an alternative to alleviate the β-carotene deficiencies in the world and especially in Africa. [ABSTRACT FROM AUTHOR]