Drought-Induced Regulatory Cascades and Their Effects on the Nutritional Quality of Developing Potato Tubers

Abstract

Competition for scarce water resources and the continued effects of global warming exacerbate current constraints on potato crop production. While plants’ response to drought in above-ground tissues has been well documented, the regulatory cascades and subsequent nutritive changes in developing tubers have been largely unexplored. Using the commercial Canadian cultivar “Vigor”, plants were subjected to a gradual drought treatment under high tunnels causing a 4 °C increase in the canopy temperature. Tubers were sampled for RNAseq and metabolite analysis. Approximately 2600 genes and 3898 transcripts were differentially expressed by at least 4-fold in drought-stressed potato tubers, with 75% and 69% being down-regulated, respectively. A further 229 small RNAs were implicated in gene regulation during drought. Expression of several small RNA clusters negatively correlated with expression of their six target patatin genes, suggesting involvement in the regulation of storage proteins during drought. The comparison of protein homologues between Solanum tuberosum L. and Arabidopsis thaliana L. indicated that down-regulated genes were associated with phenylpropanoid and carotenoid biosynthesis. As is indicative of reduced flow through the phenylpropanoid pathway, phenylalanine accumulated in drought-stressed tubers. This suggests that there may be nutritive implications to drought stress occurring during the potato tuber bulking phase in sensitive cultivars.

Mechanistic Concept of Physiological, Biochemical, and Molecular Responses of the Potato Crop to Heat and Drought Stress

“…The high respiration rate under elevated temperatures contributes to lowering potato yields [ 30 , 33 ]. Under high temperatures, the stored starch in the developing potato tuber is also utilized for respiration, contributing to a substantial decrease in the production and productivity of potato tubers [ 39 , 89 ]. Additionally, because of the high temperature, the rapid development pace results in a shortening of the entire growth cycle.…”

Whole-genome sequencing of tetraploid potato varieties reveals different strategies for drought tolerance

“…In potato, traits such as leaf area expansion, leaf senescence, partitioning of assimilates, tuber initiation and tuber growth are seriously affected by limited water supply 6 , 18 – 21 . The cascading effects of drought stress decrease protein and phenolic content of potato tubers, which reduces the benefits of potato for human nutrition 22 . Coping with drought response demands understanding complex networks of interacting genes in plants 23 , 24 .…”