DEVELOPMENTALLY REGULATED HSP40S MEDIATE DIAPAUSE AND STRESS TOLERANCE OF ARTEMIA FRANCISCANA
Female Artemia franciscana release either swimming nauplii or cysts, the latter entering a reversible state termed diapause, characterized by developmental arrest, reduced metabolism and increased stress tolerance. That cysts survive diapause is due in part to heat shock proteins (HSPs), which protect proteins from irreversible denaturation and assist in their folding, intracellular translocation or degradation. This study examines how Hsp40 affects development, diapause and stress tolerance of A. franciscana. Two Hsp40 cDNAs, ArHsp40-1 and ArHsp40-2, were cloned. The synthesis of both Hsp40s was regulated during post-diapause development of larvae and induced by stress. The ArHsp40s were individually knocked down by RNAi and cysts lacking either ArHsp40 exhibited reduced stress tolerance. Many cysts deficient in ArHsp40-1 aborted diapause and resumed growth, demonstrating a role in diapause entry. Knowing how Hsp40s influence A. franciscana development and diapause has implications in aquaculture as this organism is a common feed for commercially important species.