Identification and expression analysis of salt-responsive genes using a comparative microarray approach in Salix matsudana

Salt stress exerts negative effects on plant growth, development and yields, with roots being the primary site of both perception and damage. Salix matsudana (Chinese willow) is tolerant of high salinity. However, genes associated with this trait were rarely characterized. Therefore, we first performed salt-stress treatment on S. matsudana plants, then identified differentially expressed genes by comparison of salt-treated roots and untreated controls using microarray analysis. A total of 403 salt-responsive genes were identified, of which 239 were repressed and 164 were up-regulated. Functional classification analysis revealed that these genes belonged to families encoding proteins involved in metabolism, regulation of transcription, signal transduction, hormone responses, abiotic stress responses, and other processes related to growth and development. This suggested that when S. matsudana was confronted with salt stress, coordinated adjustments are made to physiological and biochemical processes, which would then allow more resources to be allocated to protective mechanisms to avoid salt injury. The expression patterns of representative genes were further validated and the diversity of the temporal profiles indicated that a combination of several genes and the initiation of diverse pathways performed functions in S. matsudana salt tolerance. This work represents the first study employing microarrays to investigate salt tolerance in S. matsudana. The data presented herein enhance our understanding of the molecular mechanisms of S. matsudana responses to salinity stress and lay the groundwork for genetic engineering strategies to improve stress tolerance of agronomically important species.