Overexpression of a BRASSINAZOLE RESISTANT 1 homolog attenuates drought tolerance by suppressing the expression of PLETHORA-LIKE 1 in Setaria italica

Two potential BRASSINAZOLE RESISTANT 1 (BZR1) homologs were downregulated by brassinosteroids(BRs) in Setaria italica roots.Functional analysis showed that BR regulates the dephosphorylation and nuclear localization of Si BZR1 and that Si BZR1 binds conserved BZR1-recognizing cis elements.In comparison with the wild type,Si BZR1-overexpressing S.italica seedlings were more sensitive to BR-inhibited primary root growth and drought stress,indicating that Si BZR1 is a positive regulator of BR signaling and a negative regulator of drought tolerance in S.italica.PLETHORA-LIKE 1 (Si PLT-L1) was found to be a direct target gene of Si BZR1 in S.italica roots.The expression of Si PLT-L1 was downregulated by Si BZR1.Si PLT-L1-overexpressing S.italica was less sensitive to BR-inhibited root growth and more tolerant to drought stress,possibly owing to the upregulation of drought-inducible Dehydrin-family genes.