Silver nanoparticles affect ACS expression in Tecomella undulata in vitro culture

ACC synthase, a key enzyme for the production of the simplest olefin ethylene, can regulate many aspects of the plant life cycle and is important in in vitro culture conditions. This study was carried out to shed light on the gene expression pattern of ACS in the leaves of in vitro regenerated Tecomella undulata (Roxb.) Seem. which are affected by silver nanoparticles (AgNPs). This led to a better understanding of the correlation between AgNP and regeneration. We identified a 1,216 bp fragment of the TuACS gene (JQ582835.1) containing three exons (986) and two introns (365 bp) as the first nuclear gene identified from T. undulata, along with beta-tubulin (JQ776639.1) as a house keeping gene, aimed at considering expression level of TuACS in MS media supplemented with AgNPs. Bioinformatics showed that TuACS shares a modest level of sequence similarity with other members of the PLP family, such as aspartate aminotransferase (AATase) and tyrosine aminotransferase (TATase). Visual inspection of explants grown in AgNPs media versus AgNPs free MS media revealed an increase in the mean number of fresh shoots per explants, the percentage of explants producing shoots, and plant survival. In AgNP media, TuACS expression was reduced, which may be partially responsible for the observed delayed explant senescence and increased survival under in vitro conditions. ACS promoter analysis revealed cis-acting regulatory elements such as light-responsive, hormone-responsive, and stress-responsive elements. The reduction of ACS mRNA may change the hormone balance in explants in AgNPs media. These observations suggest that AgNPs may serve to not only improve explant lifespan but increase multiplication as well.