Singh, N. P. | bioRxiv Science

bioRxiv2021

Identification of oxalyl-CoA synthetase gene (LsAAE3) and its regulatory role in β-ODAP biosynthesis in grasspea (Lathyrus sativus L.)

Grasspea is a popular pulse crop due to its hardiness and low cost of production. Presence of anti-nutritive factor {beta}-ODAP in its seeds and other plant parts hinder its widespread cultivation and usage. Oxalyl-CoA synthetase is one of the key enzyme of {beta}-ODAP biosynthesis pathway, catalyses the conversion of oxalate to oxalyl-CoA. ACYL ACTIVATING ENZYME 3 (AAE3) gene has been characterised to encode an oxalyl-CoA synthetase enzyme in many plant species. We report here the isolation of full length AAE3 homolog in grasspea with a combination of PCR based strategy and in silico analysis. We first identified AAE3 homolog by PCR using degenerate primers. The partial LsAAE3 sequence showed 88% amino acids sequence identity with the characterised AAE3 gene of M. truncatula. We then predicted the full length AAE3 sequence using the publically available transcriptome datasets of grasspea. Determination of LsAAE3 gene and protein structure and phylogenetic relationship analysis strongly suggested that LsAAE3 is a true homolog of AAE3 gene. Expression profiling of LsAAE3 in grasspea varieties with contrast in {beta}-ODAP content revealed its inverse relationship with the {beta}-ODAP content, LsAAE3 thus negatively regulates the synthesis of {beta}-ODAP. Involvement of AAE3 encoded oxalyl-CoA synthetase in a CoA-dependent pathway of oxalate degradation is well proven in many plant species. We also identified the CoA-dependent pathway of oxalate degradation in grasspea. Based on these observations, we hypothesized that LsAAE3 may regulate {beta}-ODAP content, possibly, by CoA-dependent pathway of oxalate degradation in grasspea. If this hypothesis is substantiated, genetic manipulation of LsAAE3 presents viable option for reducing {beta}-ODAP content in grass pea.

molecular biology↗

bioRxiv2020

Genome-wide binding analyses of HOXB1 revealed a novel DNA binding motif associated with gene repression

Knowledge of the diverse DNA binding specificities of transcription factors is important for understanding their specific regulatory functions in animal development and evolution. We have examined the genome-wide binding properties of the mouse HOXB1 protein in ES cells differentiated into neural fates. Unexpectedly, only a small number of HOXB1 bound regions (7%) correlate with binding of the known HOX cofactors PBX and MEIS. In contrast, 22% of the HOXB1 binding peaks display co-occupancy with the transcriptional repressor REST. Analyses revealed that co-binding of HOXB1 with PBX correlates with active histone marks and high levels of expression, while co-occupancy with REST correlates with repressive histone marks and repression of the target genes. Analysis of HOXB1 bound regions uncovered enrichment of a novel 15 base pair HOXB1 binding motif HB1RE (HOXB1 response element). In vitro template binding assays showed that HOXB1, PBX1 and MEIS can bind to this motif. In vivo, this motif is sufficient to direct expression of a reporter gene and over-expression of HOXB1 selectively represses this activity. Our analyses suggest that HOXB1 has evolved an association with REST in gene regulation and the novel HB1RE motif contributes to HOXB1 function in part through a repressive role in gene expression.

developmental biology↗