Histological analysis of somatic embryogenesis in pineapple: AcSERK1 and its expression validation under stress conditions

Somatic embryogenesis receptor-like kinase (SERK) is a small gene family found in plants. SERK is involved in somatic embryogenesis and can be found in various important signal transduction pathways. Research on SERK found in pineapple (AcSERK1 and AcSERK2) has indicated that these genes could be used as potential marker genes for monitoring the acquisition of embryogenic competence. This experiment was designed to study somatic embryogenesis in pineapple in detail using AcSERK1 as a marker gene. The results showed that somatic embryogenesis in pineapple callus originated from the surface, the inside, and the superficial layer of the callus. Very few parenchyma cells could be converted into competent cells under 2,4-D induction. The competent cells passed through the pro-embryo-protuberance, the pro-embryo, and the early stage globular embryo. The passage of competent cells through these channels formed the globular embryo. AcSERK1 expression was upregulated by jasmonic acid (JA), salicylic acid (SA), injury, and low temperature treatment. The His6-AcSERK1 protein had autophosphorylation activity. These results confirmed that AcSERK1 can be used as a marker gene for the study of embryogenesis and for expression of totipotency in pineapple. The results indicated that AcSERK1 may also play a role in pineapple stress-response signaling. For future studies, the prokaryotically-expressed His6-AcSERK1 protein can be used to examine the receptor-like kinases function of SERK proteins.