Gene Expression and Metabolite Profiling of Thirteen Nigerian Cassava Landraces to Elucidate Starch and Carotenoid Composition

Abstract

The prevalence of vitamin A deficiency in sub-Saharan Africa necessitates effective approaches to improve provitamin A content of major staple crops. Cassava holds much promise for food security in sub-Saharan Africa, but a negative correlation between β-carotene, a provitamin A carotenoid, and dry matter content has been reported, which poses a challenge to cassava biofortification by conventional breeding. To identify suitable material for genetic transformation in tissue culture with the overall aim to increase β-carotene and maintain starch content as well as better understand carotenoid composition, root and leaf tissues from thirteen field-grown cassava landraces were analyzed for agronomic traits, carotenoid, chlorophyll, and starch content. The expression of five genes related to carotenoid biosynthesis were determined in selected landraces. Analysis revealed a weak negative correlation between starch and β-carotene content, whereas there was a strong positive correlation between root yield and many carotenoids including β-carotene. Carotenoid synthesis genes were expressed in both white and yellow cassava roots, but phytoene synthase 2 (PSY2), lycopene-ε-cyclase (LCYε), and β-carotenoid hydroxylase (CHYβ) expression were generally higher in yellow roots. This study identified lines with reasonably high content of starch and β-carotene that could be candidates for biofortification by further breeding or plant biotechnological means.

Integrated Metabolomic and Transcriptomic Analyses Reveal Novel Insights of Anthocyanin Biosynthesis on Color Formation in Cassava Tuberous Roots

“…The genes from cluster C1 expressed higher in SC205 than SC9, especially during S4 to S7 stages. It seems that the genes in this cluster were not relevant to the yellow formation of cassava tuberous roots; however, a previously suggested candidate gene MeLCYE was included in this group ( 8 ). The genes from cluster C2 exhibited similar expression patterns between SC205 and SC9, i.e., the expression levels were higher at stages S1 and S2 but lower at S3 to S7.…”

“…Carotenoid synthesis genes have been demonstrated to involve in the color formation of cassava roots ( 2 , 5 , 8 ). However, the full members referred to carotenoid synthesis pathways have not yet been systematically identified and their roles in color formation remain largely unknown.…”

“…They established potential links of low transcript abundance of LCYb and HYb to the pink and yellow landraces, respectively. Similarly, Olayide et al ( 8 ) found that carotenoid biosynthesis genes were expressed in both yellow and white cassava roots. Still, only lycopene-ε-cyclase ( LCY ε), phytoene synthase 2 ( PSY2 ), and β-carotenoid hydroxylase ( CHY β) showed higher expression in yellow roots.…”

From cassava to gari: mapping of quality characteristics and end‐user preferences in Cameroon and Nigeria

“…This supports the case that it is not access to improved varieties that results into low adoption but makes a case for a large part of released varieties not living up to the quality characteristics assumed to be present in an 'improved' variety. This suggest that breeders should start evaluating their clones for characteristics preferred by end users along the food chain, through a dynamic process comparable to what has been done in heritability for starch and carotenoid composition of cassava (Olayide et al, 2020). Fliedel et al (2016) developed a new approach for providing better information to breeders early in varietal improvement programmes.…”

Understanding Biotic Stress and Hormone Signalling in Cassava (Manihot esculenta): Potential for Using Hyphenated Analytical Techniques

“…Given the successes of hyphenated techniques in delineating other biochemical processes of cassava which has been demonstrated by these studies, studies of hormonal responses of cassava to stress should surely yield results. Other studies have also been reported, including capturing biochemical diversity in cassava through the application of metabolite profiling [8]; metabolic profiles of six African cultivars of cassava (Manihot esculenta Crantz) to highlight bottlenecks of root yield [149]; photosynthesis, metabolites and soluble carbohydrates in cassava, focusing on potassium and storage root development [150]; elucidation of starch and carotenoid composition of thirteen Nigerian cassava landraces using gene expression and metabolite profiling techniques [151]. These studies support the existing reports that cassava responses to biotic and other stresses in general trigger a common cohort of responsive metabolites, providing insight into the general activation of metabolic pathways in response to stress.…”