Based on the fact that ethephon (an ethylene releaser) stimulation can significantly increase latex yield per tapping, it is traditionally believed that rubber biosynthesis is positively regulated by ethylene. Based on the critical role of jasmonic acid signaling in promoting the biosynthesis of secondary metabolites in plants, jasmonic acid signaling is also thought to play a role in the positive feedback regulation of natural rubber biosynthesis. Recent studies suggest that tapping-enhanced rubber biosynthesis is closely related to the activation of jasmonate signaling in laticifer cells of rubber tree. However, it remains unclear whether there is a crosstalk between the jasmonic acid signaling pathway and the ethylene signaling pathway in the regulation of rubber biosynthesis. For this purpose, in the present study, in vitro rubber biosynthesis efficiency of whole latex and small rubber particles (SRPs) from short rested trees treated by either methy jasmonates or ethylene were detected by using substrate ¹³C-MVA. qPCR was used to analyze the expression of four jasmonic acid signaling genes, HbCOI1, HbJAZ1, HbMYC1, HbMYC2, four ethylene-responsive element binding factors (ERFs) genes HbERFⅢa, HbERFⅦa, HbERFⅨc, HbERFⅩa, four rubber biosynthesis genes, HbHMGR1, HbSRPP1, HbREF1, HbHRT2 in laticifer cells after epicormic shoots were treated with either methy jasmonates or ethylene. The results showed that exogenous methyl jasmonate treatment significantly up-regulated the expression levels of jasmonic acid signaling genes HbCOI1, HbJAZ1, HbMYC1, HbMYC2, and rubber biosynthetic protein genes HbHMGR1, HbSRPP1, HbREF1, HbHRT2 in laticifer cells of rubber tree, and promoted rubber biosynthesis, but had little effect on the expression of ethylene-responsive element binding factor genes HbERFⅢa, HbERFⅦa, HbERFⅨc, HbERFⅩa, or even inhibited the expression. On the contrary, exogenous ethylene treatment significantly up-regulated the expression levels of ethylene-responsive element binding factor genes HbERFⅢa, HbERFⅦa, HbERFⅨc, HbERFⅩa in laticifer cells of rubber tree, but had little effect on the expression of jasmonic acid signaling genes HbCOI1, HbJAZ1, HbMYC1, HbMYC2 and rubber biosynthetic protein genes HbHMGR1, HbSRPP1, HbREF1, HbHRT2 or even inhibited the expression and rubber biosynthesis. The results suggest that there exists an antagonistic effects of jasmonic acid and ethylene on rubber biosynthesis in H. brasiliensis, which would provide a theoretical basis for elucidating the crosstalk of jasmonic acid signaling and ethylene signaling on regulation of natural rubber production.

Bougainvillea is an important woody ornamental plant in southern China. There are a large number of varieties, but the classification is relatively chaotic. This study took 133 Bougainvillea varieties introduced and preserved in Yunnan as the research object, and conducted frequency distribution statistical analysis, coefficient of variation calculation, and diversity index calculation for 10 quantitative characters and 41 discrete characters. Q-type clustering analysis was also conducted. The results showed that the 133 Bougainvillea varieties had rich diversity in many characters, and the coefficient of variation of quantitative characters ranged from 19.61%-32.59%, with an average of 26.64%. The coefficient of variation of the total flower stem length, calyx tube width, petiole length, and flower length was the highest, and the diversity index ranged from 1.69-2.09, with an average of 1.92. The diversity index of leaf length, bract width, leaf width, and bract length was the highest. The diversity index of discrete characters ranged from 0.17-2.19. There were 11 discrete characters with H′ values greater than 1, and the diversity index of bract color and calyx tube color was both greater than 2. The diversity was rich. Among the four species of Bougainvillea, the diversity index of Bougainvillea×buttiana was the highest, with the richest diversity, followed by B. peruviana, B. glabra, and B. spectabilis, whose diversity index was the lowest, with less diversity. However, each species has its own advantageous characters. Among the 51 characters, 22 characters showed significant difference among species, which were of great reference value for identifying and classifying the varieties of Bougainvillea. Based on the types of bracts, the number of spines, and the size of leaves, 133 B. varieties could be grouped into four categories: double spiny less, double spiny more, single spiny less leaflet, and single spiny large leaflet. The research results show that the phenotypic characters of the 133 B. varieties tested have high diversity, and the quantitative trait variation types are rich. This study could provide scientific basis for systematic evaluation of B. germplasm resources, variety classification, and germplasm innovation.