Dinâmica e homeostase do retroelemento Tnt1 e sua participação nas vias do etileno em plantas de Nicotiana tabacum

Abstract

It is known that expression of the Tnt1 retroelement is stress-induced, suggesting that it may play a role in plant development. To verify the dynamics and expression of Tnt1 in plants growing under homeostatic condition, we performed expression analyzes of the circadian clock genes (NtTOC1 and NtCP23), ethylene biosynthesis (ACO1 and ACO2), ethylene responsive genes (ER24, JERF1 and TEIL) and different Tnt1 regions (U3A, U3B, U3C and RT) by quantitative PCR technique (qPCR). The cDNA was produced with total RNA extracted from tobacco seedlings with 15 days of in vitro germination (9 collection points in 48 hours). qPCR were performed using Master Mix SYBR Green. The expression data were normalized through the reference gene L25, following data analysis methodology 2-ΔCt (threshold cycle). As expected, genes related to the circadian clock and ethylene biosynthesis follow a rhythmic expression. Ethylene responsive genes present a less evident rythmicity (related to the circadian cycle). Tnt1 presented great variation among the biological replicates. Although it seems to follow a cyclical expression, it seems to be displaced between days. These results suggest that although there is a basal expression of the Tnt1 subfamilies, it does not follow the circadian rhythm. Induction of Tnt1 expression by ethylene may require exposure to higher levels of the phytohormone, and in homeostasis its basal expression may be influenced by other factors that we do not yet understand.