Abstract
We evaluated differential expression of genes in leaf and xylem tissues for three Eucalyptus clones in the field using Illumina sequencing, under four contrasting fertilization regimes: a control combining nitrogen (N), phosphorus (P), and potassium (K) and three regimes with N, K, and P deficiency. The field results showed significantly better performance with a control fertilizing regime for height and circumference at 14 months, but no differences between clones. The number of up and down regulated DEG (differentially expressed genes) in pairwise clone comparisons was around 5900 for leaf and 6900 for xylem at FDR < 0.01. With fertilization treatment comparisons, DEG were only observed for N deficiency versus control with 45 up and down-regulated DEG for leaf and 1022 for xylem. The number of DEGs between fertilizer deficiency treatment and control varied greatly within each clone showing important clone by fertilization interaction. Gene ontology analysis showed that a great number of genes were related to stress, transport, and transcription factors. The co-expression analysis showed some significant correlations between complex network gene expression and tree growth induced by fertilization regime. For example, the co-expression of a 54 DEG network showed a significant correlation with tree height (0.84, P value: 1e(-04)) and DBH (0.89, P value: 7e(-06)) in the case of N deficiency versus control. Our results suggest that gene expression levels between different fertilization treatments and clones can provide a basis for future research on gene function in Eucalyptus under nutrient stress with the perspective of new development in Eucalyptus breeding.