Playing with colours: genetics and regulatory mechanisms for anthocyanin pathway in cereals

Genetic analysis of purple pigmentation in rice seed and vegetative parts - implications on developing high-yielding purple rice (Oryza sativa L.)

Pigmentation in rice grains is an important quality parameter. Purple-coloured rice (Oryza sativa L.) indicates the presence of high anthocyanin with benefits of antioxidant properties. However, the genetic mechanism of grain colour is not fully understood. Therefore, the study focused on understanding pigmentation in grain pericarp and vegetative parts, and its relationship with blast resistance and enhanced grain yield. Three local cultivars from the northeastern region (NER) of India - Chakhao Poireiton (purple), Mang Meikri (light brown), and Kala Joha (white) - along with high-yielding varieties (HYVs) Shasharang (light brown) and Sahbhagi dhan (white) were used to develop biparental populations. The findings suggested that pigmentation in vegetative tissue was governed by the inter-allelic interaction of several genes. Haplotype analysis revealed that Kala3 complemented Kala4 in enhancing purple pigmentation and that Kala4 is not the only gene responsible for purple colour as evident by the presence of a desired allele for markers RID3 and RID4 (Kala4 locus) in Chakhao Poireiton and Kala Joha irrespective of their pericarp colour, implying the involvement of some other additional, unidentified genes/loci. RID3 and RID4 together with RM15191 (Kala3 locus) could be employed as a reliable marker set for marker-assisted selection (MAS). Pericarp colour was strongly correlated with colour in different vegetative parts, but showed a negative correlation with grain yield. Pb1, reported to be associated with panicle blast resistance, contributed to leaf blast resistance. Transgressive segregants for improved pigmentation and high yield were identified. The selection of lines exhibiting coloured pericarp, high anthocyanin content, aroma, blast resistance, and increased yield compared to their respective HYV parents will be valuable resources in the rice breeding programme.

Correlation of levels of lactic acid and glucose in cerebrospinal fluid of cerebral hemorrhage patients with the occurrence of postoperative intracranial infection and clinical prognosis

Background

Cerebral haemorrhage is a critical condition that often requires surgical treatment, and postoperative intracranial infection can significantly impact patient outcomes. The aim of the study was to examine the relationship between the levels of lactic acid and glucose in cerebrospinal fluid (CSF) of patients with cerebral haemorrhage and their postoperative intracranial infection and clinical prognosis.

Methods

The study selected the clinical data of 324 patients with cerebral haemorrhage who underwent surgical treatment in our hospital from March 2020 to March 2022 for retrospective analysis and divided these patients into the intracranial infection group (Group A, n=22, leukocyte values in CSF>5×106/L) and the non-intracranial infection group (Group B, n=302, leukocyte values in CSF 5×106/L) according to the occurrence of postoperative intracranial infection in patients to detect the levels of lactic acid and glucose in CSF at different times in the two groups. Pearson method was adopted to analyze the correlation of the levels of lactic acid and glucose in CSF of patients with intracranial infection, and the Glasgow Outcome Scale (GOS) was used to assess the clinical prognosis of patients. According to their scores, these patients were divided into the good prognosis group (GPG, scores of 4-5 points, n=178) and the poor prognosis group (PPG, scores of 1-3 points, n=146). The levels of lactic acid and glucose in the CSF of patients in the two groups were measured, and the Pearson method was adopted to analyze the relationship between these levels and clinical prognosis.

Enhancing stimulation of cyaniding, GhLDOX3 activates reactive oxygen species to regulate tolerance of alkalinity negatively in cotton

Anthocyanins belong to flavonoid secondary metabolites that act as plant pigments to give flowers and fruits different colors and as "scavengers" of reactive oxygen species (ROS) to protect plants from abiotic and biotic stresses. Few studies linked anthocyanins to alkaline resistance so far. In this study, anthocyanin synthesis-related gene leucoanthocyanidin dioxygenase (LDOX) was screened as a candidate gene to explore its relationship with alkali stress. The results found that pYL156: GhLDOX3 lines treated with 50 mM Na2CO3 (pH 11.11) for 24 h showed a significant increase in peroxidase (POD) activity, a decrease in total anthocyanin content and an increase in cyanidin content and a decrease in ROS accumulation compared to pYL156. The overexpressed (OE) lines, ldox mutant and wild-type (WT) lines in Arabidopsis were treated with 50 mM Na2CO3, 100 mM Na2CO3 and 150 mM Na2CO3 for 8 d, respectively. The wilted degree of the OE lines was more severe than WT lines, and less severe in the mutant lines in the 150 mM Na2CO3 treatment. After treatment, the expression levels of AtCAT and AtGSH genes related to antioxidant system in OE lines were significantly lower than in WT, and the expression levels of AtCAT and AtGSH in mutant lines were significantly higher than in WT. In conclusion, the above results suggest GhLDOX3 played a negative regulatory role in the mechanism of resisting Na2CO3 stress. Therefore, it can be considered in cotton breeding to improve the alkali tolerance of cotton by regulating the expression of related genes.

Genetic Mapping of Flavonoid Grain Pigments in Durum Wheat

Pigmented cereal grains with high levels of flavonoid compounds have attracted the attention of nutritional science backing the development of functional foods with claimed health benefits. In this study, we report results on the genetic factors controlling grain pigmentation in durum wheat using a segregant population of recombinant inbred lines (RILs) derived from a cross between an Ethiopian purple grain accession and an Italian amber grain cultivar. The RIL population was genotyped by the wheat 25K SNP array and phenotyped for total anthocyanin content (TAC), grain color, and the L*, a*, and b* color index of wholemeal flour, based on four field trials. The mapping population showed a wide variation for the five traits in the different environments, a significant genotype x environment interaction, and high heritability. A total of 5942 SNP markers were used for constructing the genetic linkage map, with an SNP density ranging from 1.4 to 2.9 markers/cM. Two quantitative trait loci (QTL) were identified for TAC mapping on chromosome arms 2AL and 7BS in the same genomic regions of two detected QTL for purple grain. The interaction between the two QTL was indicative of an inheritance pattern of two loci having complementary effects. Moreover, two QTL for red grain color were detected on chromosome arms 3AL and 3BL. The projection of the four QTL genomic regions on the durum wheat Svevo reference genome disclosed the occurrence of the candidate genes Pp-A3, Pp-B1, R-A1, and R-B1 involved in flavonoid biosynthetic pathways and encoding of transcription factors bHLH (Myc-1) and MYB (Mpc1, Myb10), previously reported in common wheat. The present study provides a set of molecular markers associated with grain pigments useful for the selection of essential alleles for flavonoid synthesis in durum wheat breeding programs and enhancement of the health-promoting quality of derived foods.

Deciphering the Genetic Architecture of Color Variation in Whole Grain Rice by Genome-Wide Association

Whole grain rice is recommended in a natural healthy diet because of its high nutritional and healthful benefits compared to polished or white rice. The whole grain contains the pericarp with many assorted colors (such as brown, red, and black) associated with taste and commercial quality. The color attributes of whole grain or brown rice are usually undesirable and need to be improved. To decipher the genetic basis of color variation in the whole grain rice, we conducted a genome-wide association analysis of three parameters of grain colors (brightness, redness, and yellowness) in a panel of 682 rice accessions. Twenty-six loci were identified for the color parameters, implying that grain color is under polygenic control. Among them, some major-effect loci were co-localized with the previously identified genes such as Rc and Rd. To eliminate the possible mask of Rc on other loci influencing grain color, we performed the association analysis in a subset of the panel that excluded the pigmented (red and black) rice. Eighteen loci or SNPs were detected to be associated with grain color in the subpopulation, many of which were not reported before. Two significant peak SNP regions on chromosomes 1 and 9 were validated using near-isogenic lines. Based on differential expression analysis of annotated genes within the SNP regions and metabolic analysis of pooled extreme samples, we found at least three annotated genes as potential candidates involved in the flavonoid metabolic pathway related to pericarp color. These results provide insights into the genetic basis of rice grain color and facilitate genomic breeding to improve appearance and commercial quality of whole grain rice.

Integrated metabolomics and transcriptomic analysis of the flavonoid regulatory networks in Sorghum bicolor seeds

Background

The objective of this study was to reveal the flavonoid biosynthesis pathway in white (Z6), red (Z27) and black (HC4) seeds of the sweet sorghum (Sorghum bicolor) using metabolomics and transcriptomics, to identify different flavonoid metabolites, and to analyze the differentially expressed genes involved in flavonoid biosynthesis.

Results

We analyzed the metabolomics and transcriptomics data of sweet sorghum seeds. Six hundred and fifty-one metabolites including 171 flavonoids were identified in three samples. Integrated analysis of transcriptomics and metabolomics showed that 8 chalcone synthase genes (gene19114, gene19115, gene19116, gene19117, gene19118, gene19120, gene19122 and gene19123) involved in flavonoid biosynthesis, were identified and play central role in change of color. Six flavanone including homoeriodictyol, naringin, prunin, naringenin, hesperetin and pinocembrin were main reason for the color difference.

Conclusions

Our results provide valuable information on the flavonoid metabolites and the candidate genes involved in the flavonoid biosynthesis pathway in sweet sorghum seeds.

MYB-6 and LDOX-1 regulated accretion of anthocyanin response to cold stress in purple black carrot (Daucus carota L.)

AIM

Anthocyanin, an essential ingredient of functional foods, is present in a wide range of plants, including black carrots. The current investigation was carried out to analyse the effect of cold stress on the expression of major anthocyanins and anthocyanin biosynthetic pathway genes, MYB6 and LDOX-1.

METHODS AND RESULTS

Five cultivated carrot genotypes belonging to the eastern group, having anthocyanin pigment, were used in the current study. The qRT-PCR analysis revealed that relative gene expression of transcription factor MYB-6 and LDOX1gene was highly expressed upon cold stress compared to non-stress samples. High-performance liquid chromatography-based quantification of Cyanidin 3-O-glucoside (Kuromanin chloride), Ferulic acid, 3,5-Dimethoxy-4-hydroxycinnamic acid (Sinapic acid), and Rutin revealed a significant increase in these major anthocyanins in response to cold stress when compared to control plants.

CONCLUSION

We conclude that MYB6 and LDOX1 gene expression increases upon cold stress, which induces accumulation of major anthocyanins in purple black carrot and suggests a possible cross-link between cold stress and anthocyanin biosynthesis in purple black carrot.