Phosphate or nitrate imbalance induces stronger molecular responses than combined nutrient deprivation in roots and leaves of chickpea plants

The negative effects of phosphate (Pi) and/or nitrate (NO₃⁻) fertilizers on the environment have raised an urgent need to develop crop varieties with higher Pi and/or nitrogen use efficiencies for cultivation in low-fertility soils. Achieving this goal depends upon research that focuses on the identification of genes involved in plant responses to Pi and/or NO₃⁻ starvation. Although plant responses to individual deficiency in either Pi (–Pi/+NO₃⁻) or NO₃⁻ (+Pi/–NO₃⁻) have been separately studied, our understanding of plant responses to combined Pi and NO₃⁻ deficiency (–Pi/–NO₃⁻) is still very limited. Using RNA-sequencing approach, transcriptome changes in the roots and leaves of chickpea cultivated under –Pi/+NO₃⁻, +Pi/–NO₃⁻ or –Pi/–NO₃⁻ conditions were investigated in a comparative manner. –Pi/–NO₃⁻ treatment displayed lesser effect on expression changes of genes related to Pi or NO₃⁻ transport, signalling networks, lipid remodelling, nitrogen and Pi scavenging/remobilization/recycling, carbon metabolism and hormone metabolism than –Pi/+NO₃⁻ or +Pi/–NO₃⁻ treatments. Therefore, the plant response to –Pi/–NO₃⁻ is not simply an additive result of plant responses to –Pi/+NO₃⁻ and +Pi/–NO₃⁻ treatments. Our results indicate that nutrient imbalance is a stronger stimulus for molecular reprogramming than an overall deficiency.