Plant cell culture systems struggle to replicate the full spectrum of secondary metabolites found in whole plants due to the absence of organized tissue structures and specialized cell types that regulate biosynthetic pathways. Without the complex signaling networks and environmental cues present in intact plants, cultured cells often lack the necessary triggers for complete metabolite production. Additionally, the artificial growth conditions fail to simulate natural stressors like herbivory, pathogen attack, and seasonal variations that typically induce defensive compound synthesis. The homogeneous nature of cell cultures also eliminates the compartmentalization and transport mechanisms that facilitate precursor availability and metabolite accumulation in different plant organs. These limitations result in altered or reduced metabolite profiles compared to whole plants, making cell cultures useful for producing specific compounds but inadequate for capturing the complete phytochemical diversity found in nature.

Plant cell culture systems have made significant advancements in producing secondary metabolites, but they still face several limitations in replicating the full spectrum of compounds found in whole plants. Here are some key limitations:

How does the absence of environmental interactions in plant cell cultures limit the production of secondary metabolites?

Hi Abdelhak, in natural environments, plants are exposed to a variety of environmental signals, such as pathogen infection, herbivory, mechanical damage, abiotic stresses, and changes in light signals. These external stimuli activate secondary metabolic gene expression through signaling pathways such as the JA pathway, SA pathway, MAPK cascade, and light signaling pathway, thereby promoting the synthesis and accumulation of secondary metabolites.

For example, in the JA signaling pathway, mechanical damage or herbivore feeding triggers the breakdown of membrane lipids by phospholipases, leading to the production of α-linolenic acid, which is subsequently converted into jasmonic acid (JA). JA binds to its receptor COI1, which releases and activates the MYC transcription factors, ultimately initiating the biosynthesis of alkaloids, terpenoids, and other secondary metabolites.

However, in aseptic plant cell culture systems, these environmental signals are generally absent or greatly weakened, resulting in low activity of the relevant signaling pathways. For instance, the synthesis of JA is blocked, and MYC transcription factors cannot be fully activated, ultimately leading to a significant reduction in the production of secondary metabolites. This is one of the key reasons for the generally low secondary metabolic capacity observed in plant cell cultures.

How do the absence or weakening of environmental signals in aseptic plant cell culture systems impact the activation of signaling pathways and the production of secondary metabolites?