Crustacyanin has the function of binding astaxanthin which is the best antioxidant, and plays an important role in the body color variation of crustaceans. To investigate the causes of body color variation of the ridgetail white prawn, Exopalaemon carinicauda, the present study obtained four subtypes of crustacyanin gene: C1, C2, A1, and A2. Based on fluorescence quantitative polymerase chain reaction, lipocalin-C1 is mainly expressed in the eyestalk, lipocalin-C2 is in the ventral nerve cord, and lipocalin-A1 and lipocalin-A2 are in subcutaneous adipose tissues. Under the inhibiting effect of Cd 2+ stress, the expression of four subtypes first increases and then decreases within 24 h, and reaches the maximum at 6 or 12 h. RNA interference experiments showed a decrease in the expression of lipocalin genes in subcutaneous adipose tissue for each subtype, with the body color changing from transparent to red, and the dark red spots on the epidermis changing to bright red. Moreover, the blue protein in the subcutaneous adipose tissue largely disappeared, based on the light micrographs. In view of these findings, the crustacyanin gene appears to fulfill some function in the resistance to heavy metal stress and body color formation of E. carinicauda.

An efficient approach for aryl acetylene DNA-encoded library (DEL) synthesis was developed in this study by transition-metal-mediated inverse Sonogashira reaction of 1-iodoalkyne with boronic acid under ambient conditions, with moderate to excellent conversions and broad substrate adaptability for the first time. Compared to palladium-phosphine, copper iodide performed better in the on-DNA inverse Sonogashira reaction. Interestingly, substrate diversity can be enhanced by first interrogating coupling reagents under copper-promoted conditions, and then revalidating them under palladium-facilitated conditions for those reagents which failed under the former. This complementary validation strategy is particularly well-fitted to any DEL validation studies.

For the purpose of studying the epigenetic characteristics of the mitochondrial genome of the ridgetail white prawn, Exopalaemon carinicauda (Holthuis, 1950) under Cd2+ and Cr6+ heavy metal stress, the mitochondrial DNA methylation of E. carinicauda was analysed by bisulfite sequencing PCR (BSP). Many methylation sites were found at the 3′ end sequence of COX3 and at the starting region sequence of ND3, while only a few methylation sites were found at the 3′ end sequence of ND5. The mitochondrial genome was inferred to regulate the energy metabolism through the methylation process. In addition, under Cd2+ stress, mitochondrial DNA methylation was more common, and found during all stress periods (3, 6, 12, 24, 48, 72 and 96 h), while under Cr6+ stress, mitochondrial DNA methylation was less common, mainly occurring after 48 hours of stress. The sensitivity of the mitochondrial genome response to Cd2+ stress was inferred to be greater than that to Cr6+. This study revealed for the first time that methylation occurs in the mitochondrial genome of E. carinicauda in response to heavy metal stress.

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