Effects of drought stress on capsanthin during fruit development and ripening in pepper (Capsicum annuum L.)

• We found that the content of capsanthin in pepper pericarp declined with drought stress.
• Interestingly drought had no significant effect on Ccs gene expression.
• β-carotene hydroxylase (Crtz) and Lycopene-β-cyclase (Lcyb) genes of capsanthin synthesis pathway upstream were more sensitive to drought stress.
• Drought influenced expression of Lcyb and Crtz genes and influenced synthesis of capsanthin in pepper pericarp.
• Re-watering after drought stress in fruit turning stage was helpful for recovering the synthesis of capsanthin in pepper.

In recent years, soil drought has become a major bottleneck restricting the development of agriculture in the southwestern and northwestern parts of China. In these arid regions, pigment pepper cultivation has become an important local industry. The effect of drought on capsanthin production in pepper fruits has not been well studied. The aim of this work was to evaluate the effects of drought stress on capsanthin accumulation in pepper fruits, and to evaluate the effects of drought on the expression of key genes in the capsanthin biosynthetic pathway. A simple weighing method was used to adjust the pot soil water content. The water supply was controlled when fruits were at the mature-green stage on day 20 after flowering. HPLC was used to determine the fruit capsanthin content, and quantitative real-time PCR was used to quantify the expression of key genes. Cv. Yiduhong was used as a model. Our results showed that drought significantly affected capsanthin synthesis in pepper fruits; moderate to severe drought had the greatest impact on capsanthin accumulation. At the same time, we found that capsanthin levels could be restored if water was supplied to the drought-stressed plants during the stages of fruit development and ripening. Analyzing the expression of key genes in the capsanthin biosynthesis pathway indicated that drought had little effect on capsanthin/capsorubin synthase (Ccs) gene expression, but that soil drought has a greater effect on the expression of the lycopene-β-cyclase (Lcyb) and β-carotene hydroxylase (Crtz) genes, resulting in a significant reduction in the fruit capsanthin content in pepper