Transcriptional transitions in Alphonso mango (Mangifera indica L.) during fruit development and ripening explain its distinct aroma and shelf life characteristics

Abstract

Alphonso is known as the “King of mangos” due to its unique flavor, attractive color, low fiber pulp and long shelf life. We analyzed the transcriptome of Alphonso mango through Illumina sequencing from seven stages of fruit development and ripening as well as flower. Total transcriptome data from these stages ranged between 65 and 143 Mb. Importantly, 20,755 unique transcripts were annotated and 4,611 were assigned enzyme commission numbers, which encoded 142 biological pathways. These included ethylene and flavor related secondary metabolite biosynthesis pathways, as well as those involved in metabolism of starch, sucrose, amino acids and fatty acids. Differential regulation (p-value ≤ 0.05) of thousands of transcripts was evident in various stages of fruit development and ripening. Novel transcripts for biosynthesis of mono-terpenes, sesqui-terpenes, di-terpenes, lactones and furanones involved in flavor formation were identified. Large number of transcripts encoding cell wall modifying enzymes was found to be steady in their expression, while few were differentially regulated through these stages. Novel 79 transcripts of inhibitors of cell wall modifying enzymes were simultaneously detected throughout Alphonso fruit development and ripening, suggesting controlled activity of these enzymes involved in fruit softening.

The genome evolution and domestication of tropical fruit mango

“…With the Hi-C library, the purged contigs were anchored into super-scaffolds using Juicer [75] and 3d-dna pipeline [76]. ALLMAPS (version 1.0) [77] was used to anchor the Hi-C super-scaffolds with unique mapped genetic markers from the previous published mango genetic map [78]. Finally, the genome assembly contains 20 pseudochromosomal molecules, 2 organelles, and 230 unplaced scaffolds.…”

Adaptation mechanism of mango fruit (Mangifera indica L. cv. Chaunsa White) to heat suggest modulation in several metabolic pathways

“…59 The fatty acid octadecanoic acid marked the initial stages of ripening in Chaunsa mango fruit as previously reported in the mango cultivars Alphonso, Pairi and Kent. 9 At stage 5 (un-ripe fruit/79 DAF) during the development of Chaunsa mango fruit, L-alanine was the main free amino acid identied, which indicated the transition to active ripening and sweet avor development. It may be suggested that the presence of L-alanine at this stage may be due to the subsequent catabolism of g-aminobutyric acid to L-alanine by pyruvatedependent GABA transaminase (GABA-TP) in Chaunsa mango fruit.…”

“…Transcriptome studies on different mango cultivars have shown differential expression of pathways regulating the primary and secondary metabolism, such as carbohydrate metabolism, fatty acid metabolism, terpenoid backbone biosynthesis and ethylene biosynthesis. 5,9 In Arabidopsis thaliana plant, Solanum lycopersicum L., Citrus, Carrizo citrange and Cleopatra mandarin fruits, heat stress tolerance is acquired through antioxidant metabolites biosynthesized during heat stress response. 3 These antioxidant metabolites include: carbohydrates, branched-chain amino acids, fatty acids and secondary metabolites such as polyphenols, terpenoids, triterpenoids and sesquiterpenoids.…”

“…Myristic acid characterized at this stage suggests the active biosynthesis of different fatty acids. 9 Galactonic acid identied at this stage suggest the activation of galacturonate reductase and aldonolactonase which increase the ascorbate (vitamin C) level thereby regulating detoxication of ROS. 64,65 3.…”

“…4 Several studies have been carried out in mango to understand the composition and metabolism of mango leaf, 5 mango metabolic pathways, 6,7 epidermal peel transcriptome 8 and mango fruit development from inorescence up to the ripe stage. 9 In Pakistan, Sindh province is characterized by the hot semi-arid environment and moderate drought conditions. 10 During the last 5 years, South Asia has been experiencing high summer temperatures (http:// www.pmd.gov.pk and http://accuweather.com) during the mango fruit growing and harvesting months, with recurrent intense heatwaves ranging from 41 to 49 C AE 2 C from April till June.…”