[Campbell Biology P.706] Small secreted proteins SSPs in Laccaria bicolor are defined as pro... | Practice Question

Small secreted proteins SSPs in Laccaria bicolor are defined as proteins less than 100 amino acids long that fungi secrete, and their function is not yet known. Given that L. bicolor has a remarkably high number of SSP genes Table 1 and some SSP genes are highly upregulated in ectomycorrhizal mycelium Table 2 , what is the most likely general role for these SSPs in the mycorrhizal relationship?

  • A: SSPs primarily function as structural components of the fungal cell wall, strengthening the mycelium during symbiosis.
  • B: SSPs are likely involved in nutrient absorption from the soil, acting as general transporters.
  • C: SSPs facilitate communication and interaction between the fungus and the host plant, potentially mediating nutrient exchange or host immune suppression.
  • D: SSPs are waste products that the fungus excretes to reduce metabolic burden during symbiosis.

Explanation

SSPs are secreted proteins, meaning they are released outside the cell. Their high abundance in L. bicolor and significant upregulation in mycorrhizal associations strongly suggest a role in mediating interactions at the host-symbiont interface. These interactions often involve communication, nutrient exchange facilitation, or manipulation of host defenses.