The MYB gene family comprises one of the richest groups of transcription factors in plants. Plant MYB proteins are characterized by a highly conserved MYB DNA-binding domain. MYB proteins are ...classified into four major groups namely, 1R-MYB, 2R-MYB, 3R-MYB and 4R-MYB based on the number and position of MYB repeats. MYB transcription factors are involved in plant development, secondary metabolism, hormone signal transduction, disease resistance and abiotic stress tolerance. A comparative analysis of MYB family genes in rice and Arabidopsis will help reveal the evolution and function of MYB genes in plants.
A genome-wide analysis identified at least 155 and 197 MYB genes in rice and Arabidopsis, respectively. Gene structure analysis revealed that MYB family genes possess relatively more number of introns in the middle as compared with C- and N-terminal regions of the predicted genes. Intronless MYB-genes are highly conserved both in rice and Arabidopsis. MYB genes encoding R2R3 repeat MYB proteins retained conserved gene structure with three exons and two introns, whereas genes encoding R1R2R3 repeat containing proteins consist of six exons and five introns. The splicing pattern is similar among R1R2R3 MYB genes in Arabidopsis. In contrast, variation in splicing pattern was observed among R1R2R3 MYB members of rice. Consensus motif analysis of 1kb upstream region (5' to translation initiation codon) of MYB gene ORFs led to the identification of conserved and over-represented cis-motifs in both rice and Arabidopsis. Real-time quantitative RT-PCR analysis showed that several members of MYBs are up-regulated by various abiotic stresses both in rice and Arabidopsis.
A comprehensive genome-wide analysis of chromosomal distribution, tandem repeats and phylogenetic relationship of MYB family genes in rice and Arabidopsis suggested their evolution via duplication. Genome-wide comparative analysis of MYB genes and their expression analysis identified several MYBs with potential role in development and stress response of plants.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recent studies indicate that dietary fibre rich wholegrain foods exhibit low starch digestibility. Hence, resistant starch (RS) content could be an important biochemical marker for slow starch ...digestibility and hence of low glycemic index (GI) and glycemic load (GL). Rice is a starch rich grain. People consuming milled rice as a staple diet and leading sedentary life are likely to develop type-II diabetes in the long run. With rise in the number of diabetics worldwide, one possible approach is to develop rice based low GI foods with high RS content rice, as these show slow starch digestibility and hence would cause only slow rise in postprandial glucose level. In addition to amylose, the linear chains of amylopectin also influence starch digestibility. Starch debranching enzyme pullulanase (PUL) action releases a mixture of linear amylose-like chains that facilitate retrogradation of starch and synthesis of type 3 RS resulting in reduced starch digestibility. Besides mechanical processing, modern technologies like CRISPR have been used to increase amylose and RS (type 5 and type 3) content in rice making it more suitable for diabetics. Phytic acid (PA) chelates Ca++ ions required by intestinal alpha amylase and hence lowers starch digestibility.
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•Resistant starch and amylose are critical indicators for low starch digestibility.•Rice contains type 3 (retrograded) and type 5 (amylose-lipid) resistant starch.•Debranching enzyme pullulanase breaks amylopectin chain to form retrograded starch.•Phytic acid synthesized from glycolytic pathway help in lowering of glycemic index.•Starch digestibility can be regulated by mechanical and molecular approaches.
Abiotic stress tolerance is a complex trait regulated by multiple genes and gene networks in plants. A range of abiotic stresses are known to limit rice productivity. Meta-transcriptomics has emerged ...as a powerful approach to decipher stress-associated molecular network in model crops. However, retaining specificity of gene expression in tolerant and susceptible genotypes during meta-transcriptome analysis is important for understanding genotype-dependent stress tolerance mechanisms. Addressing this aspect, we describe here “abiotic stress tolerant” (ASTR) genes and networks specifically and differentially expressing in tolerant rice genotypes in response to different abiotic stress conditions. We identified 6,956 ASTR genes, key hub regulatory genes, transcription factors, and functional modules having significant association with abiotic stress–related ontologies and
cis
-motifs. Out of the 6956 ASTR genes, 73 were co-located within the boundary of previously identified abiotic stress trait–related quantitative trait loci. Functional annotation of 14 uncharacterized ASTR genes is proposed using multiple computational methods. Around 65% of the top ASTR genes were found to be differentially expressed in at least one of the tolerant genotypes under different stress conditions (cold, salt, drought, or heat) from publicly available RNAseq data comparison. The candidate ASTR genes specifically associated with tolerance could be utilized for engineering rice and possibly other crops for broad-spectrum tolerance to abiotic stresses.
Stilbenes are phytoalexins with health-promoting benefits for humans. Here, we boost stilbenes’ production, and in particular the resveratrol dehydrodimer viniferin, with significant pharmacological ...properties, by overexpressing stilbene synthase (STS) under unlimited phenylalanine (Phe) supply. Vitis vinifera cell cultures were co-transformed with a feedback-insensitive E. coli DAHP synthase (AroG*) and STS genes, under constitutive promoters. All transgenic lines had increased levels of Phe and stilbenes (74-fold higher viniferin reaching 0.74 mg/g DW). External Phe feeding of AroG* + STS lines caused a synergistic effect on resveratrol and viniferin accumulation, achieving a 26-fold (1.33 mg/g DW) increase in resveratrol and a 620-fold increase (6.2 mg/g DW) in viniferin, which to date is the highest viniferin accumulation reported in plant cultures. We suggest that this strategy of combining higher Phe availability and STS expression generates grape cell cultures as potential factories for sustainable production of stilbenes with a minor effect on the levels of flavonoids.
Stilbenes and flavonoids are two major health-promoting phenylpropanoid groups in grapes. Attempts to promote the accumulation of one group usually resulted in a decrease in the other. This study ...presents a unique strategy for simultaneously increasing metabolites in both groups in V. vinifera cv. Gamay Red grape cell culture, by overexpression of flavonol synthase (FLS) and increasing Phe availability. Increased Phe availability was achieved by transforming the cell culture with a second gene, the feedback-insensitive E. coli DAHP synthase (AroG*), and feeding them with Phe. A combined metabolomic and transcriptomic analysis reveals that the increase in both phenylpropanoid groups is accompanied by an induction of many of the flavonoid biosynthetic genes and no change in the expression levels of stilbene synthase. Furthermore, FLS overexpression with increased Phe availability resulted in higher anthocyanin levels, mainly those derived from delphinidin, due to the induction of F3′5′H. These insights may contribute to the development of grape berries with increased health benefits.
In cereals and legumes, phytic acid (PA) is the principal phosphorus reserve that serves the biosynthetic and nutritional demands of growing tissues during germination. Because of strong antioxidant ...activity and ability to chelate mineral ions, it provides several health and physiological benefits. Phytic acid is widely regarded as an anti-nutritional factor as it can bind minerals and proteins, thus decreasing their bioavailability. However, its chelating property is likely to provide several health benefits, including lowering the risk of diabetes and some malignancies, improving heart health and checking kidney stone formation. Furthermore, recent research has revealed that PA is effective against foodborne bacteria. These beneficial properties of PA open up the possibility of value-added applications in several new areas. Due to its various proven properties, PA has drawn more attention as an anti-nutrient than a beneficial compound. Nevertheless, the available food processing techniques for raw material preparation can be used to reduce the PA concentration in foods to mitigate its anti-nutritional effects. The resulting low PA products may find newer applications in the food industry. This paper aims to provide a general overview of phosphorus transport to different plant organs, biosynthesis of PA and its beneficial and anti-nutritional effects and a description of dephytinization methods.
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Taxus cell suspension culture is a sustainable technology for the industrial production of paclitaxel (Taxol®), a highly modified diterpene anti-cancer agent. The methyl jasmonate (MJ)-mediated ...paclitaxel biosynthetic pathway is not fully characterized, making metabolic engineering efforts difficult. Here, promoters of seven genes (TASY, T5αH, DBAT, DBBT, PAM, BAPT, and DBTNBT), encoding enzymes of the paclitaxel biosynthetic pathway were isolated and used to drive MJ-inducible expression of a GUS reporter construct in transiently transformed Taxus cells, showing that elicitation of paclitaxel production by MJ is regulated at least in part at the level of transcription. The paclitaxel biosynthetic pathway promoters contained a large number of E-box sites (CANNTG), similar to the binding sites for the key MJ-inducible transcription factor AtMYC2 from Arabidopsis thaliana. Three MJ-inducible MYC transcription factors similar to AtMYC2 (TcJAMYC1, TcJAMYC2, and TcJAMYC4) were identified in Taxus. Transcriptional regulation of paclitaxel biosynthetic pathway promoters by transient over expression of TcJAMYC transcription factors indicated a negative rather than positive regulatory role of TcJAMYCs on paclitaxel biosynthetic gene expression.
Fruit ripening process is associated with change in carotenoid profile and accumulation of lycopene in tomato (Solanum lycopersicum L.). In this study, we quantified the β-carotene and lycopene ...content at green, breaker and red-ripe stages of fruit ripening in eight tomato genotypes by using high-performance liquid chromatography. Among the genotypes, lycopene content was found highest in Pusa Rohini and lowest in VRT-32-1. To gain further insight into the regulation of lycopene biosynthesis and accumulation during fruit ripening, expression analysis of nine carotenoid pathway-related genes was carried out in the fruits of high lycopene genotype—Pusa Rohini. We found that expression of phytoene synthase and β-carotene hydroxylase-1 was four and thirty-fold higher, respectively, at breaker stage as compared to red-ripe stage of fruit ripening. Changes in the expression level of these genes were associated with a 40% increase in lycopene content at red-ripe stage as compared with breaker stage. Thus, the results from our study suggest the role of specific carotenoid pathway-related genes in accumulation of high lycopene during the fruit ripening processes.
Carotenoid metabolism is regulated by several genes encoding carotenoid biosynthetic pathway enzymes. In the present study, a fruit transcriptome in tomato (Solanum lycopersicum) was compared between ...high lycopene accumulating genotype EC-521086 and low lycopene accumulating genotype VRT-32-1 at three different stages (green, breaker and red) of fruit ripening. This analysis led to the identification of 2,558 differentially expressed genes at three stages of fruit ripening. Among these genes, 123 were carotenoid-correlated genes. Quantitative RT-PCR analysis revealed high expression of genes encoding enzymes involved in lycopene biosynthesis like IPP isomerase, phytoene synthase, phytoene desaturase, z-carotene desaturase; and comparatively lower expression of genes encoding enzymes involved in lycopene catabolism like lycopene cyclase, carotenoid e-ring hydroxylase, zeaxanthin epoxidase, violaxanthin de-epoxidase and neoxanthin synthase in EC-521086, thereby possibly explaining the high lycopene content in EC-521086 as compared with the low lycopene genotype VRT-32-1. Further, the EC-521086 genotype exhibited high expression of the TOMATO AGAMOUS-LIKE 1 (TAGL1) MADS box gene—a positive regulator of lycopene accumulation—at breaker stage, and low expression of the ethylene receptor LeETR4 gene—a negative regulator of trans-lycopene and β-carotene accumulation, at the red stage of fruit ripening. Our results clearly demonstrate the role of specific genes in accumulation of high lycopene in the EC-521086 tomato genotype during the fruit ripening processes.
The QlicRice database is designed to host publicly accessible, abiotic stress responsive quantitative trait loci (QTLs) in rice (Oryza sativa) and their corresponding sequenced gene loci. It provides ...a platform for the data mining of abiotic stress responsive QTLs, as well as browsing and annotating associated traits, their location on a sequenced genome, mapped expressed sequence tags (ESTs) and tissue and growth stage-specific expressions on the whole genome. Information on QTLs related to abiotic stresses and their corresponding loci from a genomic perspective has not yet been integrated on an accessible, user-friendly platform. QlicRice offers client-responsive architecture to retrieve meaningful biological information--integrated and named 'Qlic Search'--embedded in a query phrase autocomplete feature, coupled with multiple search options that include trait names, genes and QTL IDs. A comprehensive physical and genetic map and vital statistics have been provided in a graphical manner for deciphering the position of QTLs on different chromosomes. A convenient and intuitive user interface have been designed to help users retrieve associations to agronomically important QTLs on abiotic stress response in rice. Database URL: http://nabg.iasri.res.in:8080/qlic-rice/.
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