iTRAQ Protein Profile Differential Analysis between Somatic Globular and Cotyledonary Embryos Reveals Stress, Hormone, and Respiration Involved in Increasing Plantlet Regeneration of Gossypium hirsutum L.

Somatic embryo development (SED) in upland cotton shows low frequencies of embryo maturation and plantlet regeneration. Progress in increasing the regeneration rate has been limited. Here a global analysis of proteome dynamics between globular and cotyledonary embryos was performed using isobaric tags for relative and absolute quantitation to explore mechanisms underlying SED. Of 6318 proteins identified by a mass spectrometric analysis, 102 proteins were significantly up-regulated and 107 were significantly down-regulated in cotyledonary embryos. The differentially expressed proteins were classified into seven functional categories: stress responses, hormone synthesis and signal transduction, carbohydrate and energy metabolism, protein metabolism, cell wall metabolism, cell transport, and lipid metabolism. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that stress response, hormone homeostasis, and respiration and photosynthesis were involved in SED. Quantitative real-time PCR analysis co...