Search

WRKY transcription factors, which play critical roles in stress responses, have not been characterized in eggplant or its wild relative, turkey berry. The recent availability of RNA-sequencing data provides the opportunity to examine WRKY genes from a global perspective. We identified 50 and 62 WRKY genes in eggplant (SmelWRKYs) and turkey berry (StorWRKYs), respectively, all of which could be classified into three groups (I-III) based on the WRKY protein structure. The SmelWRKYs and StorWRKYs contain ~76% and ~95% of the number of WRKYs found in other sequenced asterid species, respectively. Positive selection analysis revealed that different selection constraints could have affected the evolution of these groups. Positively-selected sites were found in Groups IIc and III. Branch-specific selection pressure analysis indicated that most WRKY domains from SmelWRKYs and StorWRKYs are conserved and have evolved at low rates since their divergence. Comparison to homologous WRKY genes in Arabidopsis revealed several potential pathogen resistance-related SmelWRKYs and StorWRKYs, providing possible candidate genetic resources for improving stress tolerance in eggplant and probably other Solanaceae plants. To our knowledge, this is the first report of a genome-wide analyses of the SmelWRKYs and StorWRKYs.

A cold-tolerant line (NY-1) and a cold-sensitive cultivar (Jinyan 4) of cucumber (Cucumis sativus) were treated with temperatures of 28 degrees C/22 degrees C or 28 degrees C/12 degrees C (day/night) in a 10-h photoperiod. Carbohydrates and related enzymes were assayed from 0 to 4 h after the start of the dark period. Compared to the normal night temperature (22 degrees C, control), sucrose, stachyose and galactinol increased in mature leaves under cold-night treatment (12 degrees C) while sucrose, glucose and fructose in fruits remained unchanged. In peduncles, where stachyose is catabolized to sucrose after long-distance transport, cold nights simultaneously induced a significant increase of stachyose (substrate) and a decrease of sucrose (product), indicating that the metabolic step from stachyose to sucrose in peduncles is crucial to translocation inhibition in cold nights. This decrease was more pronounced in the cold-sensitive cultivar. Similar growth rates of fruits on one-fruit and two-fruit plants under cold-night treatment further confirmed that it is sink activity rather than source supply that is limiting the source-sink translocation. No significant genotypic differences in enzyme activities involved in the stachyose-sucrose conversion, including alkaline alpha-galactosidase, acid alpha-galactosidase, galactokinase, uridine diphosphate (UDP)-galactose pyrophosphorylase, UDP-glucose-4'-epimerase and sucrose synthase, were observed when assayed in an adenosine triphosphate (ATP)-rich in vitro environment. However, the ATP concentration was much higher in peduncles of the cold-tolerant line, indicating that a limiting ATP supply may be partially responsible for the stronger inhibition of the stachyose-sucrose pathway observed in the cold-sensitive cultivar (Jinyan 4).