Abstract
BackgroundBlueberries are one of the few horticultural crops adapted to grow in acidic soils. Neutral to basic soil pH is detrimental to all commonly cultivated blueberry species, including Vaccinium corymbosum (VC). In contrast, the wild species V. arboreum (VA) is able to tolerate a wider range of soil pH. To assess the molecular mechanisms involved in near neutral pH stress response, plants from pH-sensitive VC (tetraploid) and pH-tolerant VA (diploid) were grown at near neutral pH 6.5 and at the preferred pH of 4.5.ResultsTranscriptome sequencing of root RNA was performed for 4 biological replications per species x pH level interaction, for a total of 16 samples. Reads were mapped to the reference genome from diploid V. corymbosum, transforming ~55% of the reads to gene counts. A quasi-likelihood F test identified differential expression due to pH stress in 337 and 4867 genes in VA and VC, respectively. Both species shared regulation of genes involved in nutrient homeostasis and cell wall metabolism. VA and VC exhibited differential regulation of signaling pathways related to abiotic/biotic stress, cellulose and lignin biosynthesis, and nutrient uptake.ConclusionsThe specific responses in VA likely facilitate tolerance to higher soil pH. In contrast, response in VC, despite affecting a greater number of genes, is not effective overcoming the stress induced by pH. Further inspection of those genes with differential expression that are specific in VA may provide insight on the mechanisms towards tolerance.
Highlights
Blueberries are one of the few horticultural crops adapted to grow in acidic soils
While the vast majority of research in the topic of plant responses to soil pH has been carried out on non-calcifuge species, here we present a study comparing the transcriptomes of two congeneric plant species with contrasting soil adaptations; V. arboreum (VA) exhibits tolerance to higher pH soil while Vaccinium corymbosum (VC) is inhibited
Mapping efficiency of RNA-Seq reads to the blueberry reference genome RNA-Seq reads from two blueberry species, 207.7 million from diploid VA and 452.4 million from tetraploid VC were mapped to a reference draft genome generated for a diploid V. corymbosum [31]
Summary
Blueberries are one of the few horticultural crops adapted to grow in acidic soils. V. corymbosum (highbush blueberry, VC) is a high-value fruit crop that exhibits strict soil adaptation to acidic soils with high organic matter content [1,2,3]. These characteristics are relatively uncommon in agricultural soils, and when grown in higher pH soils, V. arboreum (sparkleberry, VA) is a wild blueberry species native to the southeastern U.S [7, 8] that, according to field observations, exhibits wider soil adaptation than VC. Other mechanisms of tolerance have yet to be proposed and tested
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