Meta-analysis of identified genomic regions and candidate genes underlying salinity tolerance in rice (Oryza sativa L.).

Rice output has grown globally, yet abiotic factors are still a key cause for worry. Salinity stress seems to have the more impact on crop production out of all abiotic stresses. Currently one of the most significant challenges in paddy breeding for salinity tolerance with the help of QTLs, is to determine the QTLs having the best chance of improving salinity tolerance with the least amount of background noise from the tolerant parent. Minimizing the size of the QTL confidence interval (CI) is essential in order to primarily include the genes responsible for salinity stress tolerance. By considering that, a genome-wide meta-QTL analysis on 768 QTLs from 35 rice populations published from 2001 to 2022 was conducted to identify consensus regions and the candidate genes underlying those regions responsible for the salinity tolerance, as it reduces the confidence interval (CI) to many folds from the initial QTL studies. In the present investigation, a total of 65 MQTLs were extracted with an average CI reduced from 17.35 to 1.66 cM including the smallest of 0.01 cM. Identification of the MQTLs for individual traits and then classifying the target traits into correlated morphological, physiological and biochemical aspects, resulted in more efficient interpretation of the salinity tolerance, identifying the candidate genes and to understand the salinity tolerance mechanism as a whole. The results of this study have a huge potential to improve the rice genotypes for salinity tolerance with the help of MAS and MABC.

Characterization of CcTFL1 Governing Plant Architecture in Pigeon pea (Cajanus cajan (L.) Millsp.).

Growth habits are among the essential adaptive traits acted upon by evolution during plant speciation. They have brought remarkable changes in the morphology and physiology of plants. Inflorescence architecture varies greatly between wild relatives and cultivars of pigeon pea. The present study isolated the CcTFL1 (Terminal Flowering Locus 1) locus using six varieties showing determinate (DT) and indeterminate (IDT) growth habits. Multiple alignments of CcTFL1 sequences revealed the presence of InDel, which describes a 10 bp deletion in DT varieties. At the same time, IDT varieties showed no deletion. InDel altered the translation start point in DT varieties, resulting in the shortening of exon 1. This InDel was validated in ten varieties of cultivated species and three wild relatives differing in growth habits. The predicted protein structure showed the absence of 27 amino acids in DT varieties, which was reflected in mutant CcTFL1 by the absence of two α-helices, a connecting loop, and shortened ß-sheet. By subsequent motif analysis, it was found that the wild-type protein had a phosphorylation site for protein kinase C, but the mutant protein did not. In silico analysis revealed that the InDel-driven deletion of amino acids spans, containing a phosphorylation site for kinase protein, may have resulted in the non-functionality of the CcTFL1 protein, rendering the determinate growth habit. This characterization of the CcTFL1 locus could be used to modulate growth habits through genome editing.

Phylogenetic analysis of phytochrome A gene from Lablab purpureus (L.) Sweet.

BACKGROUND: Phytochromes are the best characterized photoreceptors that perceive Red (R)/Far-Red (FR) signals and mediate key developmental responses in plants. It is well established that photoperiodic control of flowering is regulated by PHY A (phytochrome A) gene. So far, the members of PHY A gene family remains unexplored in Lablab purpureus, and therefore, their functions are still not deciphered. PHYA3 is the homologue of phytochrome A and known to be involved in dominant suppression of flowering under long day conditions by downregulating florigens in Glycine max. The present study is the first effort to identify and characterize any photoreceptor gene (PHYA3, in this study) in Lablab purpureus and decipher its phylogeny with related legumes. RESULTS: PHYA3 was amplified in Lablab purpureus cv GNIB-21 (photo-insensitive and determinate) by utilizing primers designed from GmPHYA3 locus of Glycine max. This study was successful in partially characterizing PHYA3 in Lablab purpureus (LprPHYA3) which is 2 kb longer and belongs to exon 1 region of PHYA3 gene. Phylogenetic analysis of the nucleotide and protein sequences of PHYA genes through MEGA X delineated the conservation and evolution of Lablab purpureus PHYA3 (LprPHYA3) probably from PHYA genes of Vigna unguiculata, Glycine max and Vigna angularis. A conserved basic helix-loop-helix motif bHLH69 was predicted having DNA binding property. Domain analysis of GmPHYA protein and predicted partial protein sequence corresponding to exon-1 of LprPHYA3 revealed the presence of conserved domains (GAF and PAS domains) in Lablab purpureus similar to Glycine max. CONCLUSION: Partial characterization of LprPHYA3 would facilitate the identification of complete gene in Lablab purpureus utilizing sequence information from phylogenetically related species of Fabaceae. This would allow screening of allelic variants for LprPHYA3 locus and their role in photoperiod responsive flowering. The present study could aid in modulating photoperiod responsive flowering in Lablab purpureus and other related legumes in near future through genome editing.

Allelic characterization and protein structure analysis reveals the involvement of splice site mutation for growth habit differences in Lablab purpureus (L.) Sweet.

BACKGROUND: Interrelationship between growth habit and flowering played a key role in the domestication history of pulses; however, the actual genes responsible for these traits have not been identified in Indian bean. Determinate growth habit is desirable due to its early flowering, photo-insensitivity, synchronous pod maturity, ease in manual harvesting and short crop duration. The present study aimed to identify, characterize and validate the gene responsible for growth habit by using a candidate gene approach coupled with sequencing, multiple sequence alignment, protein structure prediction and binding pocket analysis. RESULTS: Terminal flowering locus was amplified from GPKH 120 (indeterminate) and GNIB-21 (determinate) using the primers designed from PvTFL1y locus of common bean. Gene prediction revealed that the length of the third and fourth exons differed between the two alleles. Allelic sequence comparison indicated a transition from guanine to adenine at the end of the third exon in GNIB 21. This splice site single-nucleotide polymorphism (SNP) was validated in germplasm lines by sequencing. Protein structure analysis indicated involvement of two binding pockets for interaction of terminal flowering locus (TFL) protein with other proteins. CONCLUSION: The splice site SNP present at the end of the third exon of TFL locus is responsible for the transformation of shoot apical meristem into a reproductive fate in the determinate genotype GNIB 21. The splice site SNP leads to absence of 14 amino acids in mutant TFL protein of GNIB 21, rendering the protein non-functional. This deletion disturbed previously reported anion-binding pocket and secondary binding pocket due to displacement of small ß-sheet away from an external loop. This finding may enable the modulation of growth habit in Indian bean and other pulse crops through genome editing.

Associating gene expressions with curcuminoid biosynthesis in turmeric.

BACKGROUND: Biologically important curcuminoids viz curcumin, demethoxycurcumin, and bisdemethoxycurcumin in turmeric rhizome have several health benefits. Pharmaceutical industries synthesize curcuminoids manipulating gene expressions in vitro or in vivo because of their medicinal importance. In this experiment, we studied the gene expressions involved in the curcuminoid biosynthesis pathway in association with curcuminoid yield in turmeric rhizome to study the impact of individual gene expression on curcuminoid biosynthesis. RESULTS: Gene expressions at the different growth stages of turmeric rhizome were association tested with respective curcuminoid contents. Gene expression patterns of diketide-CoA synthase (DCS) and multiple curcumin synthases (CURSs) viz curcumin synthase 1 (CURS1), curcumin synthase 2 (CURS2), and curcumin synthase 3 (CURS3) were differentially associated with different curcuminoid contents. Genotype and growth stages showed a significant effect on the gene expressions resulting in a significant impact on curcuminoid balance in turmeric rhizome. DCS and CURS3 expression patterns were similar but distinct from CURS1 and CURS2 expression patterns in turmeric rhizome. DCS expression had a significant positive and CURS3 expression had a significant negative association with curcumin, demethoxycurcumin, bisdemethoxycurcumin, and total curcuminoid in turmeric rhizome. CURS1 expression had a negative association with curcumin whereas CURS2 expression showed a positive association with demethoxycurcumin. CONCLUSIONS: The effects of DCS and CURS expressions are not always positive with different curcuminoid contents in turmeric rhizome. DCS expression has a positive and CURS3 expression has a negative association with curcuminoids. CURS1 and CURS2 are also associated with curcumin and demethoxycurcumin synthesis. This mechanism of co-expression of diketide-CoA synthase and multiple curcumin synthases in turmeric rhizome has a significant effect on curcuminoid balance in different turmeric cultivars. Further experiment will explore more insights; however, association-based test results from this experiment can be useful in improving curcuminoid yield in turmeric rhizome or in vitro through the application of genetic engineering and biotechnology. Associating gene expressions with curcuminoid biosynthesis in turmeric.