Overexpression of BnKCS1-1, BnKCS1-2, and BnCER1-2 promotes cuticular wax production and increases drought tolerance in Brassica napus

Higher amounts of cuticular wax in plants have been associated with improved plant stress tolerance and increased potential for industrial use. In this study, orthologs of KCS1 and CER1 in Arabidopsis, designated BnKCS1-1, BnKCS1-2, and BnCER1-2, were isolated from Brassica napus. Transcription of BnKCS1-1 and BnKCS1-2 in B. napus were induced by abscisic acid (ABA) and drought treatment, while transcription of BnCER1-2 was induced only by drought treatment. All three gene transcripts decreased significantly when plants were treated with methyl jasmonate (MeJA) or subjected to cold stress. Overexpression of BnKCS1-1, BnKCS1-2, and BnCER1-2 under the control of the CaMV35S promoter led to a significant increase in cuticular wax on transgenic B. napus leaves. BnKCS1-1 and BnKCS1-2 overexpression led to similar differences from non-transformed plants, with significantly higher levels of aldehydes (C29 and C30), alkanes (C28, C29, and C31) and secondary alcohols (C28 and C29), and a significantly lower level of C29 ketone. Overexpression of BnCER1-2 led to an increase in alkanes (C27, C28, C29, and C31), a decrease in secondary alcohols (C28 and C29), and insignificant changes in other wax components. Scanning electron microscopy revealed that overexpression of BnKCS1-1, BnKCS1-2, and BnCER1-2 in B. napus resulted in a higher density of wax crystals on the leaf surface than observed in non-transformed plants. Transgenic plants showed a reduced rate of water loss and increased drought tolerance compared to non-transformed plants. These results suggest that BnKCS1-1, BnKCS1-2, and BnCER1-2 gene products can modify the cuticular wax of B. napus. Changing cuticular waxes using transgenic approaches is a new strategy for genetic improvement of plant drought tolerance and provides an opportunity for development of B. napus as a surface-wax crop.