Analysis Of Physiology And Transcriptome Of Pistil Of Oil Palm After Pollination

Palm oil,the product of oil palm(Eleis guineensis Jacq.)is one of the main sources of Chinese edible oil,but in China,palm oil highly depends on import,so it is necessary to breed new varieties that can adapt to Chinese environment.Pollination and fertilization is closely related to fruit yield and seed formation.Various substances,especially hormones,are involved in a series of life activities,including plant pollination process,stimulating flower growth,controlling fruit growth and development and so on.Oil palm is a heterotypic crop.The study of pistil development after pollination of oil palm can provide a theoretical basis for the improvement of seed setting rate and the development of breeding.In this study,the main cultivar Tenera was used as the experimental material.The pistils at different time points after pollination were collected,and the physiological and biochemical indexes including the contents of osmotic substances,endogenous hormones,antioxidant substances and activity were measured to explore the effects that pollination has on the changes of these substances.Transcriptome sequencing techniques was utilized to reveal how pollination affects a wide range of substances at the molecular level.The results are as follows:(1)After pollination,the content of malondialdehyde(MDA)in the pistiles of oil palm showed a single peak,with a growth rate of 36.92% at the 4 h after pollination compared with that without pollination,which was significantly different from other time points except the 72 h.The activity of catalase(CAT)reached the peak at the 4th after pollination.The activity of peroxidase(POD)decreased rapidly within 1 h until 12 h after pollination,which was considerably lower than that before pollination,and was significantly higher than that at the 72 h after inoculation.The activity of superoxide dismutase(SOD)showed 2 peaks,which appeared at the 1 h and the 8 h.Total phenol(TP)content reached two peaks at the 2 h and the 12 h after pollination,and the TP content at 48 h after pollination was lower than that without pollination.The content of soluble sugar(SS)and soluble protein(SP)showed an opposite trend,the former increased first and then decreased,while the latter decreased first and then increased.The content of proline(Pro)rised in volatility.The content of indole-3-acetic acid(IAA)and zeatin riboside(ZR)showed similar bimodal changes.The trend of abscisic acid(ABA)content was opposite to them.In the process of pollination and fertilazation of oil palm pistils,higher energy substance content,antioxidant substance content and(IAA+ZR)/ABA ratio were beneficial to pollination and fertilization.In the process of production,exogenous hormones can be used to promote and increase the success rate of pollination.(2)The transcriptome sequencing analysis of pistils at different time points after pollination revealed that there were 1419 common differential genes,385 common upregulated genes and 1033 common down-regulated genes at 2 h,4 h,12 h,24 h,and 48 h after pollination compared with non-pollination.Most of the differentially expressed genes after pollination are related to substance metabolism,regulation of hormone levels,oxidation-reduction reaction,biosynthesis of amino acids,etc.It can be inferred that the most important effects of pollination on pistil are energy substances,hormones and cellular respiration.(3)Differential genes related to IAA signaling pathway and metabolic pathway after pollination mostly belong to the ARF,SAUR and AUX/IAA families.Some genes of the ARF family,AUX/IAA family and TIR1 family involved in pollination were more active when IAA content was high,suggesting that these genes may have participated in the negative regulation of IAA.In addition,the expression quantity of Eg FPT1(LOC105048317)、Eg FPT2(LOC105047748)genes of AUX/IAA family and Eg FPT3(LOC105059115)gene of SAUR family during pollination were much higher than that of other genes of the same family,which might be closely related to the pollination process.In plants,the signaling system of cytokinin is a complex two-component signaling system.In the experiment,the number of differential genes belonging to the B-ARR family was the largest,and most of those with higher expression and active changes belonged to the A-ARR and B-ARR families.The variation laws of expression quantity of some genes in CKX family are opposite,and different genes in this family may have different ways of acting in the process of cytokinin degradation.In this study,the ABA signal transduction pathways of PYR/PYL/RCAR and PP2 C families were observed to have a large number of different genes.(4)There were 55 AUX/IAA family genes identified in oil palm,and the upstream contained many plant hormone response elements,indicating that the content of IAA in oil palm was controlled by various hormones.The genes of group B of the AUX/IAA family were more highly expressed than group A in the process of oil palm pollination.The respective roles of several hormones in the process of pollination and fertilization,as well as the interaction mechanism and molecular mechanism between various hormones still need to be further studied and explored.The functions of several genes screened in this paper in the process of pollination and fertilization still need to be further studied and demonstrated.