Background Heat treatment is widely used to break dormancy for seed germination and phytohormones could be deeply involved. However, effect of heat treatment on phytohormone related genes/proteins/metabolites and possible relationship with dormancy release remains unclear in oil palm. In this study, oil palm seeds were heat-treated at 39 °C for 60 days according to the method for commercial production. The embryos of seeds during heat treatment (0 d, 15 d, 30 d, 45 d and 60 d) and of germinated seeds (70 d and 75 d) were selected to discover the mechanisms involved in oil palm seed germination. RNA-seq and iTRAQ were applied to investigate DEGs and DEPs related to seed germination; qPCR and western blot were used as validation accordingly; endogenous phytohormones were determined by LC-MS/MS and exogenous phytohormones were also applied to validate their effects on seed germination. Results RNA-seq results showed that plant hormone signal transduction was one of the most important pathways and eight phytohormones involved, while six of them (ABA, GA, ET, CTK, IAA and JA) were also identified by iTRAQ. Both RNA-seq and iTRAQ results showed that the expression of ABA decreased after heat treatment, which was further validated by qPCR and western blot. Furthermore, changes in endogenous phytohormones showed that ABA decreased rapidly to about 9% of the control at 30 d and then stayed at very low levels until germination; GA and CTK increased while IAA was not affected by heat treatment. Besides, exogenous ABA treatments (10, 100, 1000 mg/L) showed that the germination rate decreased to 63, 42 and 16% of the control, respectively, suggesting that ABA suppress seed germination and the inhibition effect increase with higher concentration; while the germination rates of exogenous GA and IAA treatments barely changed among different concentrations. Conclusions Phytohormones are deeply involved in oil palm seed germination and ABA acts as an inhibitor. Heat treatment can eliminate endogenous ABA and break dormancy, while GA and CTK may also involve in dormancy release. At least 30 days of heat treatment might be necessary. This study provided informative perspectives on oil palm seed germination, which could be also applicable in other palm species. Electronic supplementary material The online version of this article (10.1186/s12870-019-1970-0) contains supplementary material, which is available to authorized users.

Commercially important palms (oil palm, coconut, and date palm) are widely grown perennial trees with tremendous commercial significance due to food, edible oil, and industrial applications. The mounting pressure on the human population further reinforces palms’ importance, as they are essential crops to meet vegetable oil needs around the globe. Various conventional breeding methods are used for the genetic improvement of palms. However, adopting new technologies is crucial to accelerate breeding and satisfy the expanding population’s demands. CRISPR/Cas9 is an efficient genome editing tool that can incorporate desired traits into the existing DNA of the plant without losing common traits. Recent progress in genome editing in oil palm, coconut and date palm are preliminarily introduced to potential readers. Furthermore, detailed information on available CRISPR-based genome editing and genetic transformation methods are summarized for researchers. We shed light on the possibilities of genome editing in palm crops, especially on the modification of fatty acid biosynthesis in oil palm. Moreover, the limitations in genome editing, including inadequate target gene screening due to genome complexities and low efficiency of genetic transformation, are also highlighted. The prospects of CRISPR/Cas9-based gene editing in commercial palms to improve sustainable production are also addressed in this review paper.

Haustorium absorbs energy from the endosperms (liquid and solid) and plays a key role in nutrient mobilization during coconut germination and seedling growth. This study was conducted to shed light on possible interactions between haustorium and endosperms during this process. Germination rates and morphological changes of coconut cultivars Hainan Tall (HT) and Red Dwarf (RD), as well as the profiles of sugars and fatty acids in endosperms and haustorium were also analyzed. Results showed that liquid and solid endosperm inside the coconut exhausts successively, while haustorium occupies the nut gradually. Haustorium had significant positive correlation with seedling, while it had significant negative correlation with liquid and solid endosperms. Sugars in liquid endosperm continuously decreased, whereas in solid endosperm and haustorium accumulated at early stages and decreased later along with the aggressive seedling growth. Fatty acids in solid endosperm shared a very similar trend with sugars. In conclusion, haustorium development and seedling growth mainly depend on the nutrients stored in the liquid endosperm at early stages and then depend on the solid endosperm, in which fatty acids degrade rapidly to sugar so as to provide enough energy. These findings could be applicable in coconut germination and seedling propagation. Core Ideas Relative cool season (25–29°C) is more suitable for coconut germination and local variety (HT) is more adaptable. Development mainly depends on stored nutrients in liquid endosperm at early stages and then on solid endosperm. Fatty acids in solid endosperm degrade rapidly to sugars since liquid endosperm almost exhausted. Conversion of fatty acids to sugars helps provide enough energy for rapidly growing haustorium and seedling.