Expression of the lycopene-e-cyclase LCYE gene correlates with the content of b-carotene and chlorophylls in maize vegetative tissue

Maize ( Zea mays L.) is an important world crop. One of the valuable traits of this plant is the biosynthesis of vitamin A precursors in kernel (dietary nutrition) and photosynthetic tissue (protection of the plant from stress; silage with increased dietary value). The amount of synthesized provitamin A in kernel depends on the level of expression of the lycopene-ε-cyclase LcyE gene, which catalyzes the formation of α-carotene and is involved in the regulation of the ratio of b-b and b-e fluxes of carotenoid metabolism. The aim of the study was to analyze the correlation between the content of the sum of carotenoids, β-carotene, and chlorophylls a and b with the expression of the LcyE gene in the leaves of inbred maize lines of domestic selection. To achieve the goal, four inbred maize lines were used in the study: three white-grained (6097-1, MBK and Shumny's Tetraploid) and one (5580-1) with yellow grain color. Expression of the LcyE gene in leaves was determined by quantitative real-time PCR. Quantitative determination of the amount of carotenoids, chlorophylls a and b, and β-carotene in leaves was carried out spectrophotometrically using the Folch method. Correlations between pigment content and LcyE gene expression were evaluated using statistical methods. As a result, we assessed a possible correlation between the activity of the LcyE gene and the content of carotenoids and chlorophylls in the photosynthetic tissue of four maize lines: three white-grained (6097-1, MBC and Shumnoy Tetraploid) and one (5580-1) with yellow-colored kernel. Quantification of carotenoids revealed the highest content of these pigments in the leaves of the Tetraploid Shumny line. The accessions of the remaining three lines synthesized a smaller amount of carotenoids and were similar to each other in this parameter. At the same time, β-carotene, as well as chlorophylls a and b, were most of all contained in the leaves of line 6097-1 - approximately 2 times more than in other analyzed lines, where the pigment content did not differ significantly. Thus, the absence of associations between the color of the kernel and the content of the b-carotene and sum of carotenoids in maize leaves was confirmed. On the other hand, the obtained data suggest a positive relationship between the amount of β-carotene and chlorophylls (a and b). It is possible to assume an increased rate of photosynthesis in the photosynthetic tissues of line 6097-1 in comparison with other analyzed maize lines. Accordingly, line 6097-1 may have an increased resistance to oxidative stress, as well as be a donor of a trait with an increased content of provitamin A (as a silage crop). The expression of the lycopene-e-cyclase LycE gene was determined in the same leaf tissues. It was shown that the LycE gene was expressed ~ 4-5 times higher in the leaves of accessions of lines 5580-1 and Tetraploid Shumny than in the leaves of accessions of lines MBK and 6097-1. Correlation analysis showed an inverse relationship between the content of b-carotene and chlorophylls (a and b) and the level of LycE gene expression. Thus, in this study, for the first time, we assessed a possible correlation between the activity of the LcyE gene and the content of carotenoids and chlorophylls in the photosynthetic tissue of white and yellow grain maize lines of domestic selection. No associations were found between grain color and the content of total carotenoids and β-carotene in maize leaves. A positive relationship was found between the amount of β-carotene and chlorophylls a and b. For the first time, an inverse relationship between the content of β-carotene and chlorophylls a and b and the level of LycE gene expression was determined. The possibility of using data on the expression of the LycE gene in the leaf as an expression molecular marker of the amount of provitamin A synthesized in the leaves, as well as the degree of plant resistance to photooxidative stress, was demonstrated. The data obtained can be used in maize breeding to search for donors of the trait of increased content of provitamin A in the leaves.