Abstract
MicroRNAs (miRNAs) and endogenous small interfering RNAs (siRNAs) are key players in plant stress responses. Here, we present the sRNA transcriptomes of mangroves Bruguiera gymnorrhiza and Kandelia candel. Comparative computational analyses and target predictions revealed that mangroves exhibit distinct sRNA regulatory networks that differ from those of glycophytes. A total of 32 known and three novel miRNA families were identified. Conserved and mangrove-specific miRNA targets were predicted; the latter were widely involved in stress responses. The known miRNAs showed differential expression between the mangroves and glycophytes, reminiscent of the adaptive stress-responsive changes in Arabidopsis. B. gymnorrhiza possessed highly abundant but less conserved TAS3 trans-acting siRNAs (tasiRNAs) in addition to tasiR-ARFs, with expanded potential targets. Our results indicate that the evolutionary alteration of sRNA expression levels and the rewiring of sRNA-regulatory networks are important mechanisms underlying stress adaptation. We also identified sRNAs that are involved in salt and/or drought tolerance and nutrient homeostasis as possible contributors to mangrove success in stressful environments.
Highlights
SRNA profiles have been embodied in the unique mangrove “lifestyle”
We demonstrated the differential expression of miRNAs between mangroves and glycophytes, which resembled the adaptive responses of these miRNAs under various abiotic stresses
Most importantly, altered expression of these miRNAs largely resembles the miRNA expression changes that confer enhanced stress tolerance in Arabidopsis (Fig. 4), suggesting that evolutionary changes in miRNA expression may contribute to mangrove adaptations to high-salinity and low-fertility environments
Summary
SRNA profiles have been embodied in the unique mangrove “lifestyle”. How could the distinct mangrove sRNA profiles shed light on the molecular mechanisms underlying plant stress adaptations? Only red sea mangrove (Avicennia marina) miRNAs have been identified by high-throughput sequencing[14]. Information on sRNA expression profiles is scarce for most mangrove species. No attempt has been made to compare the mangrove sRNA repertoire with that of stress-sensitive plants. We deep sequenced the sRNA libraries from the leaf and flower tissues of Bruguiera gymnorrhiza and Kandelia candel, two viviparous and salt-excluding mangrove species. We demonstrated the differential expression of miRNAs between mangroves and glycophytes, which resembled the adaptive responses of these miRNAs under various abiotic stresses. MiRNA target prediction and the expanded features of putative tasiRNAs reveal the rewiring of the sRNA regulatory networks in mangroves
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