Ultraviolet-B signalling: Arabidopsis brassinosteroid mutants are defective in UV-B regulated defence gene expression.
The involvement of brassinosteroids in signalling events in plants during UV-B stress (280-315 nm) was investigated in Arabidopsis thaliana. Brassinosteroids are involved in growth and development in plants and have also been shown to enhance stress tolerance. Three mutants deficient in the biosynthetic pathway of brassinolide (BL; det2, dim1 and cpd) and the BL insensitive mutant (bri1) were together with visible light irradiated with 3 or 9 h of UV-B radiation (biologically effective radiation normalised to 300 nm being 0.24 W m(-2)). Also, a small size control, irx1, and Columbia 0 (Col-0) wild-type plants were examined under identical conditions. Gene expression patterns were established for these mutants with a set of four molecular markers (the defence genes chalcone synthase (CHS), PYROA, pathogenesis-related protein PR-5, and a gene regulated by very low levels of UV-B, MEB5.2). Although the genes in the brassinodefective mutants were still induced by UV-B radiation, they all also showed reduced levels of mRNA transcripts compared with Col-0 and irx1. The bri1 and cpd were the mutants with lowest levels of molecular marker mRNA transcripts. The effects of impairment of brassinosteroid signalling also differed between the genes studied, indicating a need for a complete brassinosteroid pathway in UV-B signalling.
Department of Natural Sciences, Orebro University, 701 82 Orebro, Sweden.
Helena
H
Sävenstrand
Mikael
M
Brosché
Ake
A
Strid
D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects*; D060406:Brassinosteroids; D002777:Cholestanols / Q000378:metabolism* / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D013260:Steroids, Heterocyclic / Q000378:metabolism* / Q000528:radiation effects; D014466:Ultraviolet Rays
D060406:Brassinosteroids; D002777:Cholestanols; D013260:Steroids, Heterocyclic; C023623:brassinolide