Research by a team led by Hainan University professor Shi Haitao into how heatshock protein 90 co-chaperone modules fine-tune the antagonistic interaction between salicylic acid and auxin biosynthesis in cassava was published in Cell Reports on Feb 2.

Heat shock protein 90 is an important molecular chaperone in plants. However, HSP90-mediated plant immune response remains elusive in cassava. In Shi’s study, cassava bacterial blight induces the expression of MeHsf8, which directly targets MeHSP90.9 to activate its expression and immune response. Further identification of SHI-related sequence 1 (MeSRS1) and MeWRKY20 as MeHSP90.9 co-chaperones revealed the underlying mechanism of MeHSP90.9-mediated immune response.

Illustration of the thesis.

MeHSP90.9 interacts with MeSRS1 and MeWRKY20 to promote the transcriptional activation of salicylic acid biosynthetic gene avrPphB Susceptible 3 (MePBS3) and tryptophan metabolic gene N-acetylserotonin O-methyltransferase 2 (MeASMT2), respectively to activate SA biosynthesis but inhibit tryptophan-derived auxin biosynthesis.

Notably, genetic experiments confirmed that overexpressing MePBS3 and MeASMT2 could rescue the effects of silencing MeHsf8-MeHSP90.9 on disease resistance. The study highlights the dual regulation of SA and auxin biosynthesis by MeHSP90.9, providing a mechanistic understanding of MeHSP90.9 client partners in plant immunity.