Final answer:
During the unfolded protein response, heat shock proteins (HSPs) and components of the ubiquitin-proteasomal degradation pathway, such as the COP9 signalosome subunit 6, are upregulated to assist in refolding or degrading misfolded proteins. Additionally, proteins related to hormone metabolism and signaling, particularly ethylene and abscisic acid pathways, are also upregulated.
Step-by-step explanation:
The unfolded protein response (UPR) is a cellular mechanism that deals with stress in the endoplasmic reticulum (ER) when misfolded or unfolded proteins accumulate. During the UPR, several processes are upregulated to restore normal function of the cell. This includes the increased transcription and activity of heat shock proteins (HSPs), which assist in the refolding of misfolded proteins. Heat shock proteins are released from the NR/HSP complex in response to stress such as increased temperature, and their genes are also transcribed more actively.
Another key player in the UPR is the ubiquitin-proteasomal degradation pathway. While no significant changes in the ubiquitin-activating (E1), -conjugating (E2), or -ligase (E3) enzymes were detected in Al-treated tomato radicles, the COP9 signalosome (CSN) subunit 6 was induced. CSN regulates the function of ubiquitin E3, playing an essential role in DNA damage response, cell cycle control, and gene expression, as well as in response to environmental stimuli and stress.
Furthermore, proteins involved in hormone metabolism and signaling pathways are also upregulated, influencing the biosynthesis and signaling processes for hormones like ethylene and abscisic acid (ABA). Conversely, proteins involved in the jasmonate pathway are repressed in the tomato radicles subjected to aluminum stress.