Homeologous genes involved in mannitol synthesis reveal unequal contributions in response to abiotic stress in Coffea arabica

Abstract

Polyploid plants can exhibit transcriptional modulation in homeologous genes in response to abiotic stresses. Coffea arabica, an allotetraploid, accounts for 75% of the world's coffee production. Extreme temperatures, salinity and drought limit crop productivity, which includes coffee plants. Mannitol is known to be involved in abiotic stress tolerance in higher plants. This study aimed to investigate the transcriptional responses of genes involved in mannitol biosynthesis and catabolism in C. arabica leaves under water deficit, salt stress and high temperature. Mannitol concentration was significantly increased in leaves of plants under drought and salinity, but reduced by heat stress. Fructose content followed the level of mannitol only in heat-stressed plants, suggesting the partitioning of the former into other metabolites during drought and salt stress conditions. Transcripts of the key enzymes involved in mannitol biosynthesis, CaM6PR, CaPMI and CaMTD, were modulated in distinct ways depending on the abiotic stress. Our data suggest that changes in mannitol accumulation during drought and salt stress in leaves of C. arabica are due, at least in part, to the increased expression of the key genes involved in mannitol biosynthesis. In addition, the homeologs of the Coffea canephora subgenome did not present the same pattern of overall transcriptional response, indicating differential regulation of these genes by the same stimulus. In this way, this study adds new information on the differential expression of C. arabica homeologous genes under adverse environmental conditions showing that abiotic stresses can influence the homeologous gene regulation pattern, in this case, mainly on those involved in mannitol pathway.

Transcriptome Analysis of Leaves, Flowers and Fruits Perisperm of Coffea arabica L. Reveals the Differential Expression of Genes Involved in Raffinose Biosynthesis

“…eugenioides subgenome (CaCe) instead of those from C . canephora (CaCc), as previously described for the citric acid cycle [63] and mannitol biosynthesis [64]. …”

Transcriptome analysis in Coffea eugenioides, an Arabica coffee ancestor, reveals differentially expressed genes in leaves and fruits

“…In another work, when the CaWRKY1a and CaWRKY1b genes that encode for transcription factors involved in the coffee defense responses to abiotic and biotic stresses were concomitantly expressed, both homeologous genes were found to contribute to the overall transcriptional level (Petitot et al 2008). Given the regulation mechanisms between homeologous genes, these studies and others (Carvalho et al 2014;Cotta et al 2014) demonstrated the complexity of regulation in allopolyploids and indicated that genes useful for C. arabica breeding programs could be present in its genome but have become inactive due to partitioned expression. However, one of the drawbacks of these studies was the lack of C. eugenioides data, which was necessary to increase and improve the comparison of gene expression of these subgenomes.…”

“…Primers were designed using Primer Express v.3.0 (Applied Biosystems), and qPCRs were run in a 7500 Fast Real-Time PCR System (Applied Biosystems) using the SYBR Green PCR Master Mix (Applied Biosystems). We followed the basic qPCR procedure described in a previous publication on coffee plants (Carvalho et al 2014).…”

Spatiotemporal expression patterns of wheat amino acid transporters reveal their putative roles in nitrogen transport and responses to abiotic stress

“…One single or two homeologs were often predominantly expressed under normal and stress conditions. The uneven contribution of homeologs involved in mannitol synthesis has been reported in Coffea arabica 60 and the expression of the alcohol dehydrogenase A (AdhA) gene homeologs in allotetraploid cotton diverged significantly under multiple stresses 61 . The specific expression of homeologs during organ development and in response to stress conditions may benefit polyploid plants by allowing additional flexibility of response at the transcript level.…”