Gene transcripts responsive to drought stress identified in Citrus macrophylla bark tissue transcriptome have a modified response in plants infected by Citrus tristeza virus

Citrus macrophylla Wester (CM) has valuable agronomic characteristics such as the ability to grow in saline soils, although with low tolerance to prolonged drought stress (DS). To understand the mechanisms that characterize CM response to water scarcity, this study compared transcriptome profile changes in CM stem tissue when exposed to DS and identified a total of 2745 differentially expressed transcripts (DETs, fold change > 2), of which 631 were up-regulated and 2114 were down-regulated. DETs up-regulated by DS were enriched in pathways such as the redox and osmotic system or soluble carbohydrates and in transcripts for low molecular weight proteins such as late embryogenesis abundant protein (LEA). Down-regulated transcripts were mainly assigned to photosynthesis, transport, phenylpropanoids, calcium dependent kinases, brassinosteroids and other hormones including salicylic acid and abscisic acid. To assess the interplay between DS and Citrus tristeza virus (CTV) infection, twelve genes were profiled by quantitative Real-Time PCR (qPCR) analysis in control and CTV-infected CM plants, with or without DS. The twelve analyzed transcripts were significantly correlated (r = 0.82, p < 0.001) with the RNA-Seq results and gave insight into the responses of CM to drought and/or to infection with CTV. Transcriptome results unveiled highly responsive genes to DS in stem tissue, which may be candidates for genetic selection of high drought tolerant plants of CM.

Automated summary

This study investigated the transcriptome changes in Citrus macrophylla in response to drought stress and identified thousands of differentially expressed transcripts. The results showed that drought stress can induce the up- and down-regulation of various genes in the stem tissue of Citrus macrophylla, some of which may be associated with drought tolerance in this species.