Abstract
Plant regeneration via somatic embryogenesis (SE) is the key step for genetic improvement of cotton (Gossypium hirsutum L.) through genetic engineering mediated by Agrobacteria, but the molecular mechanisms underlying SE in cotton is still unclear. Here, RNA-Sequencing was used to analyze the genes expressed during SE and their expression dynamics using RNAs isolated from non-embryogenic callus (NEC), embryogenic callus (EC) and somatic embryos (SEs). A total of 101, 670 unigenes were de novo assembled. The genes differentially expressed (DEGs) amongst NEC, EC and SEs were identified, annotated and classified. More DEGs were found between SEs and EC than between EC and NEC. A significant number of DEGs were related to hormone homeostasis, stress and ROS responses, and metabolism of polyamines. To confirm the expression dynamics of selected DEGs involved in various pathways, experiments were set up to investigate the effects of hormones (Indole-3-butytric acid, IBA; Kinetin, KT), polyamines, H2O2 and stresses on SE. Our results showed that exogenous application of IBA and KT positively regulated the development of EC and SEs, and that polyamines and H2O2 promoted the conversion of EC into SEs. Furthermore, we found that low and moderate stress is beneficial for proliferation of EC and SEs formation. Together, our global analysis of transcriptomic dynamics reveals that hormone homeostasis, polyamines, and stress response synergistically regulating SE in cotton.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-016-0511-6) contains supplementary material, which is available to authorized users.
Highlights
Crop losses due to multiple stresses have been predicted to be much greater than previously estimated in the coming future, especially due to climate change and industry development (Chen et al 2015)
Our results showed that exogenous application of indole-3-butyric acid (IBA) and KT positively regulated the development of embryogenic callus (EC) and somatic embryogenesis (SE), and that polyamines and H2O2 promoted the conversion of EC into SEs
Arabidopsis thaliana plants transformed with the SOMATIC EMBRYOGENESIS R ECEPTOR -LIKE KINASE 1(AtSERK1) gene showed a marked increase in SE compared to wild-type cultures (Hecht et al 2001)
Summary
Crop losses due to multiple stresses have been predicted to be much greater than previously estimated in the coming future, especially due to climate change and industry development (Chen et al 2015). For the majority of crops, Agrobacterium-mediated transformation is the method of choice for genetic modification. The prerequisite of this method is to have a highly efficient and. Many studies have investigated physiological and biochemical changes during SE in various plant species with a focus on understanding the mechanisms of gene regulation related to SE. These efforts identified genes differentially expressed in somatic embryos (SEs), highlighted the pathways likely to be involved in SE and discovered molecular or protein markers for SE (Mantiri et al 2008). Medicago truncatula SOMATIC EMBRYO RELATED FACTOR1 (MtSERF1) is essential for somatic embryo development and is induced by ethylene (Mantiri et al 2008)
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