Biology subjects

Naik, J.

Publications and source records attributed to Naik, J..

4 recordsLinked to original sources

bioRxiv2023

The HSF-DREB-MYB regulatory module regulates flavonol biosynthesis and flavonoid B-ring hydroxylation in banana

Plant flavonols act primarily as ultraviolet radiation absorbers, reactive oxygen species scavengers, and phytoalexins, and they contribute to biotic and abiotic stress tolerance in plants. Banana (Musa acuminata), an herbaceous monocot and important fruit crop, accumulates flavonol derivatives in different organs, including the edible fruit pulp. Although flavonol content varies greatly in different organs, the molecular mechanisms involving transcriptional regulation of flavonol synthesis in banana are not known. Here, we characterized three SG7-R2R3 MYB transcription factors (MaMYBFA1, MaMYBFA2, and MaMYBFA3) and their upstream regulators, heat shock transcription factor (MaHSF11) and dehydration responsive element binding factor (MaDREB1), to elucidate the molecular mechanism involved in transcriptional regulation of flavonol biosynthesis in banana. MaMYBFA positively regulate flavonol synthase 2 (MaFLS2) and downregulates MaFLS1. We show these transcription factors to be weak regulators of flavonol synthesis. Overexpression of MaHSF11 enhances flavonol contents, particularly that of myricetin, and promotes flavonol B-ring hydroxylation, which contributes to the diversity of flavonol derivatives. MaHSF11 directly interacts with the MaFLS1 and flavonoid 3', 5'-hydroxylase1 (MaF3'5'H1) promoters, both in vitro and in vivo. MaHSF11 activates the expression of MaDREB1 directly, which in turn regulates the expression of MaMYBFA3. Overall, our study elucidates a novel regulatory mechanism for flavonol synthesis in banana and suggests possible targets for genetic optimization to enhance nutritional value and stress responses in this globally important fruit crop. Significance statementOur study reveals that the three stress-responsive SG7 MYB factors, MaMYBFA1-3, are modest regulators of flavonol biosynthesis in banana. In contrast, the drought- and heat-responsive MaHSF11 plays a strong, positive role in this pathway, enhancing flavonol biosynthesis and flavonoid B-ring hydroxylation by upregulating key biosynthetic genes, such as MaFLS1 and MaF35H1, as well as MaDREB1, another regulator of flavonol biosynthesis in banana.

plant biology↗

bioRxiv2022

Mrj an Hsp40 family chaperone regulates oligomerization of Orb2 and long-term memory

Orb2 the Drosophila homolog of Cytoplasmic polyadenylation element binding protein (CPEB) forms prion-like oligomers. These oligomers consist of Orb2A and Orb2B isoforms and their formation are dependent on the oligomerization of the Orb2A isoform. Drosophila with a mutation diminishing Orb2As prion-like oligomerization forms long-term memory but fails to maintain it over time. Since, this prion-like oligomerization of Orb2A plays a crucial role in the maintenance of memory, here we aim to find what regulates this oligomerization. In an immunoprecipitation-based screen, we identify interactors of Orb2A in the Hsp40 and Hsp70 families of proteins. Amongst these, we find an Hsp40 family protein Mrj as a regulator of the conversion of Orb2A to its prion-like form. Mrj interacts with Hsp70 proteins and acts as a chaperone by interfering with the aggregation of pathogenic Huntingtin. Unlike its mammalian homolog, we find Drosophila Mrj is neither an essential gene nor causes any gross neurodevelopmental defect. We observe a loss of Mrj results in a reduction in Orb2 oligomers. Further, the knockdown of Mrj in the mushroom body neurons results in a deficit in long-term memory. Our work implicates a chaperone Mrj in mechanisms of memory regulation through controlling the oligomerization of Orb2A and its association with the translating polysomes.

neuroscience↗

bioRxiv2022

Flavonols contrary affect the interconnected glucosinolate and camalexin biosynthesis pathway in Arabidopsis thaliana

Flavonols are structurally and functionally diverse molecules playing roles in plant biotic and abiotic stress tolerance, auxin transport inhibition, pollen development, etc. Despite their ubiquitous occurrence in land plants and multifunctionality, the effect of perturbation of flavonol biosynthesis over global gene expression and pathways other than flavonoid biosynthesis has not been studied in detail. To understand the signaling role of different flavonol metabolites, herein, we used the flavonol deficient Arabidopsis thaliana loss-of-function mutant flavonol synthase1 (fls1-3) as object of study. Comparative transcriptome and metabolic profiling were used to study the effects of genetic flavonol deficiency and exogenous supplementation with flavonol derivatives (kaempferol, quercetin and rutin) on different cellular processes in the seedling. Various flavonol biosynthesis-related regulatory and structural genes were found to be up-regulated in the fls1-3 mutant which could be reversed by exogenous flavonol feeding. Our manifold comparative studies indicated the modulation of various biological processes and metabolic pathways by flavonols. Camalexin biosynthesis was found to be negatively regulated by flavonols. Interestingly, flavonols appeared to promote the accumulation of aliphatic glucosinolate through transcription factor-mediated up-regulation of biosynthesis genes. Overall, this study provides new insights into molecular mechanisms by which flavonols interfere with the relevant signal chains and their molecular targets and adds new knowledge to the expanding plethora of biological activity of flavonols in plants. SignificanceComparative transcriptome and metabolomic profiling of genetic flavonol deficiency and exogenous flavonol supplementation in A. thaliana seedlings, for the first-time revealed the inverse regulation of interconnected specialized metabolite pathways by flavonol aglycones, and -glycosides. Flavonols negatively regulate camalexin biosynthesis, while promoting the accumulation of aliphatic glucosinolates. Our study adds new insights into the expanding plethora of biological activity of flavonols in plants and will help to uncover the molecular mechanisms by which flavonols interfere with the relevant signal chains and their molecular targets.

plant biology↗

bioRxiv2022

Interplay between R2R3 MYB-type activators and repressors regulates proanthocyanidin biosynthesis in banana (Musa acuminata)

O_LIProanthocyanidins are oligomeric flavonoid pigments that promote plant disease resistance and benefit human health. However, the transcriptional regulatory network that fine-tunes proanthocyanidin biosynthesis in banana (Musa acuminata) fruit remains poorly understood. C_LIO_LIWe characterized two proanthocyanidin-specific R2R3 MYB activators (MaMYBPA1-MaMYBPA2) and four repressors (MaMYBPR1-MaMYBPR4) to elucidate the mechanisms underlying the transcriptional regulation of proanthocyanidin biosynthesis in banana. C_LIO_LIHeterologous expression of MaMYBPA1 and MaMYBPA2 partially complemented the Arabidopsis thaliana proanthocyanidin-deficient transparent testa2 mutant. MaMYBPA1 and MaMYBPA2 interacted physically with MaMYCs and bound the promoters of the genes encoding anthocyanin synthase, leucoanthocyanidin reductase, and anthocyanidin reductase in vitro and form functional MBW complexes with MaTTG1 in A. thaliana protoplasts to transactivated these promoters in vivo. C_LIO_LIOverexpression of MaMYBPAs alone or with MaMYC in banana fruits induced proanthocyanidin accumulation and the transcription of proanthocyanidin biosynthesis- related genes. MaMYBPR repressors are also shown to interact with MaMYCs, forming repressing MBW complexes, and diminished proanthocyanidin accumulation. Interestingly the overexpression of MaMYBPA induces the expression of MaMYBPR, indicating an agile regulation of proanthocyanidin biosynthesis via the formation of competitive MBW complex. Taken together, our results reveal regulatory modules of R2R3 MYB- that fine-tune proanthocyanidin biosynthesis and offer possible targets for genetic manipulation in banana. C_LI

plant biology↗