Changes in Tomato Gene Expression during Potato Spindle Tuber Viroid Infection Reveal a Complex Array of Changes Affecting Brassinosteroid Synthesis and Signaling

摘要

Viroids like Potato spindle tuber viroid (PSTVd) are the smallest known agents of infectious disease - small, highly structured, circular RNA molecules that lack detectable messenger RNA activity yet are able to replicate autonomously and cause disease in susceptible plant species. To better understand the role of different hormone signaling pathways in disease induction, microarray analysis was used to compare changes in tomato gene expression associated with PSTVd infection in two tomato cultivarsplus a third transformed line expressing small PSTVd siRNAs in the absence of viroid replication. Changes in mRNA levels for the sensitive cultivar 'Rutgers' were extensive, involving more than half of the ca. 10,000 genes present on the array. Effects on mRNAs encoding enzymes involved in gibberellin and brassinosteroid biosynthesis were accompanied by numerous changes affecting their respective signaling pathways. In the dwarf cultivar 'MicroTom', a marked up-regulation of genes involved in response to stress and other stimuli was observed only when exogenous brassinosteroid was applied to infected plants, thereby providing the first evidence for the involvement of brassinosteroid-mediated signaling in viroid disease induction.