The drought response of potato reference cultivars with contrasting tolerance
Systems responses to drought stress of four potato reference cultivars with differential drought tolerance (Solanum tuberosum L.) were investigated by metabolome profiling and RNA sequencing. Systems analysis was based on independent field and greenhouse trials. Robust differential drought responses across all cultivars under both conditions comprised changes of proline, raffinose, galactinol, arabitol, arabinonic acid, chlorogenic acid and 102 transcript levels. The encoded genes contained a high proportion of heat shock proteins and proteins with signalling or regulatory functions, for example, a homolog of abscisic acid receptor PYL4. Constitutive differences of the tolerant compared with the sensitive cultivars included arbutin, octopamine, ribitol and 248 transcripts. The gene products of many of these transcripts were pathogen response related, such as receptor kinases, or regulatory proteins, for example, a homolog of the Arabidopsis FOUR LIPS MYB-regulator of stomatal cell proliferation. Functional enrichment analyses imply heat stress as a major acclimation component of potato leaves to long-term drought stress. Enhanced heat stress during drought can be caused by loss of transpiration cooling. This effect and CO2 limitation are the main consequences of drought-induced or abscisic acidinduced stomatal closure. Constitutive differences in metabolite and transcript levels between tolerant and sensitive cultivars indicate interactions of drought tolerance and pathogen resistance in potato.