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

Abstract

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. 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 (17.92-45.35µg∙g-1); there was no difference between stems (5.67-12.75µg∙g-1) and fruit (6.18-12.53µg∙g-1). The highest β-carotene content was in accessions 'GBK027049' (12.53-45.35µg∙g-1) and '453B' (6.18-32.09µg∙g-1). The PSY and PDS expressions were positively correlated with amount of β-carotene in leaves, stems, and fruits. 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.