In Arabidopsis, the HEAT-INDUCED TAS1 TARGET2 (HTT2) is an important
thermotolerance gene that is silenced by ta-siR255, an siRNA. This ta-siR255
siRNA is absent from heading Chinese cabbage (Brassica rapa ssp.
pekinensis). The team of Jianxia Jiang from Chinese Academy of Sciences
previously attempted to overexpress the heading Chinese cabbage BrpHTT2 gene
but failed due to cosuppression.
The researchers aimed to overexpress an exogenous HTT2, the Arabidopsis
HTT2, in heading Chinese cabbage to improve its thermotolerance. After
transforming the Arabidopsis HTT2 to heading Chinese cabbage, the
researchers evaluated the transformed plants under high-temperature (38°C)
and heat-shock (46°C) conditions.
The survival rate of the transformed seedlings increased compared to
wildtypes under heat shock. The hypocotyl length of the transformed
seedlings were also increased under high temperature and heat shock. Several
heat-shock factor genes were also found to be upregulated in the transformed
plants under high-temperature and heat shock conditions. In the field, the
transgenic plants appeared greener and formed leafy heads earlier than
The study provides a new approach to the genetic manipulation of
thermotolerance in crops through the introduction of exogenous genes.