Differences in fennel seed responses to drought stress at the seed formation stage in sensitive and tolerant genotypes

To understand the effects of drought on fennel seed production and determine the underlying molecular processes, various fennel genotypes were exposed to drought stress. The yield and quality, including aromatic oil content, of fennel seeds were reduced by drought during seed development. To explore drought-induced biological processes in fennel, a label-free/gel-free proteomic analysis was performed. In Gaziantep and Tatmaj cultivars, which are sensitive and tolerant fennel genotypes, respectively, 106 and 92 drought-responsive proteins were identified. Comparison of protein-functional profiles indicated that proteins classified in stress, cell, and protein synthesis/degradation categories consisted important responsive mechanisms against drought stress. Pathway analysis visualized that the tricarboxylic acid cycle is important for both cultivars. In Tatmaj, moderate activation of proteins related to oxidative pentose phosphate pathway was detected along with an increase in photosynthesis-related proteins. Furthermore, cluster analysis of drought-responsive proteins using protein abundance at milky, dough, and mature stages identified protein homeostasis as a mechanism of drought tolerance in fennel. These results suggest that coordinated energy consumption and supply might be a drought-tolerance mechanism in fennel plants.