Suboptimal temperature effect on expression of genes involved in auxin transport and signaling in tomato root

Auxin is a central hormone that exerts pleiotropic effects on plant growth including the development of shoots, roots, and other organs under normal condition or stress. In this study, the transcripts change of AUX/IAA, ARF, BRX and PIN4 which involve in auxin transporter and signaling were evaluated in root of tolerant and sensitive tomato genotypes under 15°C. AUX/IAA4 which is a negative regulator of auxin response genes was strongly up regulated in tolerant genotype at 15°C however, the transcript level of this gene was decreased in sensitive genotype. ARF and PIN4 were highly up regulated by suboptimal temperature in sensitive genotype whereas they were down regulated in tolerant genotype in recovery time (2 hours). The expression pattern of BREVIS RADIX (BRX) gene as a common point of interaction of auxin and brassinosteroids suggested that the BRX gene under sub optimal temperature in sensitive genotype was up regulated and reached the maximum level after 2h transfer to 23°C. The results of this study show that auxin concentration is increased in sensitive genotype and it induced the ARF, PIN4 and BRX whereas AUX/IAA4 was repressed. The results of common motifs in 1500 bp of upstream revealed that the AATAT motif of PRISM algorithm was frequency observed in all genes.