Translational control of gene expression in plant development and stress response

According to the central dogma of molecular biology, RNA levels should directly correlate with protein expression. However, empirical data from both plant and animal systems often reveal a weak correspondence between these molecular entities. This study reevaluates transcriptomic and proteomic datasets from Arabidopsis thaliana cotyledons and hypocotyls to illustrate instances of uncoupled transcript and protein levels. This phenomenon extends beyond developmental biology into stress response mechanisms. Analysis of the aquaporin gene AtPIP2F in Arabidopsis demonstrates a similar disjunction between RNA and protein expression, paralleled by the homologous gene VviPIP2;2 in Vitis vinifera (grapevine), where aquaporins play a pivotal role in managing hydraulic conductance and root water uptake under water stress conditions. Despite these parallels, the underlying reasons for the weak correlation in gene expression remain elusive. To delve into the regulatory mechanisms, polysome profiling was employed on Arabidopsis seedlings and Vitis vinifera leaves, focusing on translational control during development and in response to drought stress, respectively. The results indicate significant translational differences between cotyledons and hypocotyls of Arabidopsis, yet individual gene translation remained consistent across developmental stages. In Arabidopsis, AGO1 deficiency causes malformed leaves and sterile flowers. AGO1, regulated by miR168, plays a role in RNA silencing. miR168 binds to polysomes at day 6 but not at day 10, yet AGO1 protein levels decrease by day 10, suggesting complex regulation. In Vitis vinifera, the translation of aquaporin genes VviPIP2-5 and VviTIP2-1 was notably suppressed under drought conditions but showed recovery upon rehydration, underscoring the role of translational regulation in stress adaptation. This thesis elucidates the intricacies of post-transcriptional regulation, providing insights into the discordance between transcript and protein levels, and highlighting novel layers of gene expression control in plant development and stress response.