Aluminum Responsive Genes in Flax (Linum usitatissimum L.)

Abstract

Flax (Linum usitatissimum L.) is a multipurpose crop which is used for the production of textile, oils, composite materials, pharmaceuticals, etc. Soil acidity results in a loss of seed and fiber production of flax, and aluminum toxicity is a major factor that depresses plant growth and development in acid conditions. In the present work, we evaluated gene expression alterations in four flax genotypes with diverse tolerance to aluminum exposure. Using RNA-Seq approach, we revealed genes that are differentially expressed under aluminum stress in resistant (Hermes, TMP1919) and sensitive (Lira, Orshanskiy) cultivars and selectively confirmed the identified alterations using qPCR. To search for differences in response to aluminum between resistant and sensitive genotypes, we developed the scoring that allowed us to suggest the involvement of MADS-box and NAC transcription factors regulating plant growth and development and enzymes participating in cell wall modifications in aluminum tolerance in flax. Using Gene Ontology (GO) enrichment analysis, we revealed that glutathione metabolism, oxidoreductase, and transmembrane transporter activities are the most affected by the studied stress in flax. Thus, we identified genes that are involved in aluminum response in resistant and sensitive genotypes and suggested genes that contribute to flax tolerance to the aluminum stress.

Figure 1

Expression alterations of 7 genes in flax cultivars Hermes, TMP1919, Lira, and Orshanskiy under aluminum exposure at low pH evaluated by high-throughput sequencing (a) and qPCR (b).

Figure 2

Expression patterns for genes participating in water transmembrane transporter activity (GO 0005372) in flax cultivars Lira, Orshanskiy, Hermes, and TMP1919 under control conditions and aluminum exposure. The heatmap represents Z-scores of normalized read counts per million (CPM) for each gene: from blue (low expression level) to orange (high expression level). Row names show top BLAST hits of the assembled gene transcripts.

Figure 3

Expression alterations in flax plants under aluminum exposure in Lira, Orshanskiy, Hermes, and TMP1919 cultivars for genes involved in oxidoreductase activity (GO 0016491). Each heatmap row corresponds to one gene (total 21 000 genes). Color scale represents the binary logarithm of expression level fold change (aluminum exposure/control conditions) from -2 (i.e., 4-fold downregulation, blue) to +2 (4-fold upregulation, red).