Background: Codon usage bias (CUB) analysis is an effective method for studying specificity, evolutionary relationships, and mRNA translation and discovering new genes among various species. In general, CUB analysis is mainly performed within one species or between closely related species and no such study has been applied among species with distant genetic relationships. Here, seven Rosales species with high economic value were selected to conduct CUB analysis. Results: The results showed that the average GC1, GC2 and GC3 contents were 51.08, 40.52 and 43.12%, respectively, indicating that the A/T content is more abundant and the Rosales species prefer A/T as the last codon. Neutrality plot and ENc plot analysis revealed that natural selection was the main factor leading to CUB during the evolution of Rosales species. All 7 Rosales species contained three high-frequency codons, AGA, GTT and TTG, encoding Arg, Val and Leu, respectively. The 7 Rosales species differed in high-frequency codon pairs and the distribution of GC3, though the usage patterns of closely related species were more consistent. The results of the biclustering heat map among 7 Rosales species and 20 other species were basically consistent with the results of genome data, suggesting that CUB analysis is an effective method for revealing evolutionary relationships among species at the family or order level. In addition, chlorophytes prefer using G/C as ending codon, while monocotyledonous and dicotyledonous plants prefer using A/T as ending codon. Conclusions: The CUB pattern among Rosales species was mainly affected by natural selection. This work is the first to highlight the CUB patterns and characteristics of Rosales species and provides a new perspective for studying genetic relationships across a wide range of species.

Identifying the appropriate harvesting stage of jujube fruit is of high interest since the changes in physiological indicators during the fruit maturation may influence the fruit nutritional quality. The present study aimed at assessing the effect of the maturation stages on the nutritional composition and quality of the Chinese jujube variety ‘Dongzao.’ Fresh fruits were harvested at three consecutive maturity stages: white (W), semi-red (SR), and full-red (R) stage, for analyzing a wide range of nutritional constituents. Our results showed significant effects of the maturity stage on the fruit nutritional constituents. Soluble sugars and dietary fibers (mainly lignin and hemicellulose) highly increased in the fruit. Total flavonoids, carotenoids, and saponin contributing to the antioxidant capacity of the fruit were fairly decreased over the maturity stages. Except for citric, ascorbic, and succinic acids, all the organic acids increased in the fruit. Interestingly, jujube fruit is a good source of essential amino acids (26% of the total amino acids), and also gradually accumulated cyclic nucleotides (cAMP and cGMP) during the maturation. From our results, the semi-red stage seems to be the most appropriate for harvesting the jujube fruit in order to preserve its bioactive compounds.

Chinese jujube (Ziziphus jujuba Mill.) and its wild ancestor, sour jujube (Z. acidojujuba C.Y. Cheng & M.J. Liu), is a Ziziphus genus in the Rhamnaceae family. ZJ and ZA are rich in a variety of active ingredients, with triterpenoids being a unique active ingredient, which are present in the fruit, leaves, branches, and roots. More than 120 triterpenoids have been identified in ZJ and ZA, and have various biological activities. For example, betulinic and ursolic acids have anticancer, antioxidant, antibacterial and antiviral activities. ceanothic, alphitolic, and zizyberanalic acids possess anti-inflammatory activities. The MVA pathway is a synthetic pathway for triterpenoids in ZJ and ZA, and 23 genes of the MVA pathway are known to regulate triterpene synthesis in ZJ and ZA. In order to better understand the basic situation of triterpenoids in ZJ and ZA, this paper reviews the types, content dynamic changes, activities, pharmacokinetics, triterpenoid synthesis pathways, and the effects of domestication on triterpenoids in ZJ and ZA, and provides some ideas for the future research of triterpenoids in ZJ and ZA. In addition, there are many types of ZJ and ZA triterpenoids, and most of the studies on their activities are on lupane- and ursane-type triterpenes, while the activities of the ceanothane-type and saponin are less studied and need additional research.