Characterization of factors underlying the metabolic shifts in developing kernels of colored maize

Abstract

Elucidation of the metabolic pathways determining pigmentation and their underlying regulatory mechanisms in maize kernels is of high importance in attempts to improve the nutritional composition of our food. In this study, we compared dynamics in the transcriptome and metabolome between colored SW93 and white SW48 by integrating RNA-Seq and non-targeted metabolomics. Our data revealed that expression of enzyme coding genes and levels of primary metabolites decreased gradually from 11 to 21 DAP, corresponding well with the physiological change of developing maize kernels from differentiation through reserve accumulation to maturation, which was cultivar independent. A remarkable up-regulation of anthocyanin and phlobaphene pathway distinguished SW93 from SW48, in which anthocyanin regulating transcriptional factors (R1 and C1), enzyme encoding genes involved in both pathways and corresponding metabolic intermediates were up-regulated concurrently in SW93 but not in SW48. The shift from the shikimate pathway of primary metabolism to the flavonoid pathway of secondary metabolism, however, appears to be under posttranscriptional regulation. This study revealed the link between primary metabolism and kernel coloration, which facilitate further study to explore fundamental questions regarding the evolution of seed metabolic capabilities as well as their potential applications in maize improvement regarding both staple and functional foods.

Intra-Kernel Reallocation of Proteins in Maize Depends on VP1-Mediated Scutellum Development and Nutrient Assimilation

“…This discrepancy was confirmed by previous transcriptome analyses: The expression of Vp1 is initiated at ;3 to 5 DAP, reaches a peak at ;10 DAP, and gradually decreases thereafter until the end of grain filling (Supplemental Figure 8; Chen et al, 2014;Meng et al, 2018;Yi et al, 2019). By contrast, C1 and Em genes begin to express from ;12 to 15 DAP (McCarty et al, 1991;Hu et al, 2016), and Glb1 and Glb2 are increased in expression from ;20 DAP (Figure 2; Supplemental Figure 8). The discrepant temporal-expression trends among these genes suggest that perhaps some unknown factors rather than VP1 directly promote initiation of C1, Em, and Glbs expression.…”

Isolation and Characterization of Three Chalcone Synthase Genes in Pecan (Carya illinoinensis)

“…In Brunfelsia acuminata , the expression of BaCHS was positively correlated with petal anthocyanin contents [39]. In a maize cultivar, ‘SW93′ (purple kernels), two CHSs were upregulated along the kernel as the color deepened and anthocyanins accumulated [40]. In C. sinensis , high CHS transcript values were associated with a high amount of total tea polyphenols and total catechin [41,42].…”

The Application of Metabolomics for the Study of Cereal Corn (Zea mays L.)

“…The integration of transcriptomic data revealed that kinetic trends in the transcriptome and metabolome were similar across kernel development. An important metabolic shift from the primary to the secondary metabolism occurred at 16 DAP only in the purple pigmented kernel targeting the biosynthesis of anthocyanins and precursors of phlobaphenes [113]. The biochemical information generated in above studies would be valuable in molecular breeding strategies aimed at increasing health promoting metabolites such as anthocyanins in corn kernel.…”

“…Hu et al [ 113 ] studied the metabolome of purple pigmented and non-pigmented kernels from China at different maturity stages (11, 16, 21 days after pollination (DAP)) using a combination of LC-MS/MS and GC-MS. A total of 247 metabolites were identified and metabolomes differed according to the maturity stage. The integration of transcriptomic data revealed that kinetic trends in the transcriptome and metabolome were similar across kernel development.…”