Recently, the research group of Jiang Shuling from Institute of Pomology, Chinese Academy of Agricultural Sciences (IPCAAS), the research group of Li He from Shenyang Agricultural University, along with the experts from Egypt and Saudi Arabia, jointly published a research paper titled "Ppbbx24-del mutant positively regulates light induced anthocyanin accumulation in the ‘Red Zaosu’pear ( Pyrus pyrifolia  White Pear Group)" online in the Chinese Academy of Sciences Q1 Journal of Integrated Agriculture. The paper analyzed the regulatory mechanism of the mutated Ppbbx24-del  gene in the accumulation of anthocyanins in ‘Red Zaosu’ pear.

Red pears are highly favored by consumers due to their beautiful appearance and rich nutrition. However, few red pear varieties are widely cultivated in production, especially the crispy flesh type Eastern pear varieties, the fruits are often difficult to color, and the coloring level is also unstable in different regions and cultivation conditions, and the full red varieties are extremely rare. Exploring the key genes and analyzing the formation mechanism of red trait are great significant for red pear breeding and cultivation regulation. ‘Red Zaosu’ is a crispy red sport variety identified from the high-quality crispy flesh pear variety ‘Zaosu’, and is an excellent material for studying pear coloring.

Previously, the research team identified a mutated Ppbbx24-del gene in the ‘Red Zaosu’ pear, which is closely related to its coloration (Ou et al., 2020). On this basis, this article further studied the expression characteristics of PpBBX24  and its mutant gene Ppbbx24-del , as well as their action mechanism in the accumulation of anthocyanins in ‘Red Zaosu’ pear. The results showed that light was necessary in the fruit coloring of ‘Red Zaosu’ pear, but could not affect the expression of PpBBX24  and its mutant gene Ppbbx24-del , and there was no significant difference in the expression of the two genes in the skin of ‘Red Zaosu’ pear; The transient over-expression of Ppbbx24-del gene in pear peel and stable over-expression in tobacco and pear callus tissues indicated Ppbbx24-del has the ability to promote anthocyanin accumulation, while PpBBX24  does not; Due to the premature termination of the coding sequence of P pbbx24-del  gene, the C-terminus of its encoded protein is missing two key domains, NLS and VP. Its subcellular localization was changed from nuclear localization to nuclear cytoplasmic co-localization; PpBBX24 could interact with the anthocyanin accumulation related transcription factor PpHY5 and bind to the G-Box domain in the promoters of anthocyanin synthesis and regulation related genes such as PpCHS , PpCHI , and PpMYB10 , inhibiting the activation effect of PpHY5 on these gene promoters; However, Ppbbx24-del could not interact with PpHY5, but could also bind to the G-Box domain in the promoters of the aforementioned genes, and activate these promoters together with PpHY5. The individual activation effect of Ppbbx24-del was much greater than that of PpHY5, which was the fundamental reason for the reddening of the ‘Red Zaosu’ pear peel and young leaves. In summary, this study drew a model diagram of Ppbbx24-del regulating the accumulation of anthocyanins in ‘Red Zaosu’ pear, and systematically analyzed the molecular mechanism of the mutated Ppbbx24-del regulating the accumulation of anthocyanins in ‘Red Zaosu’ pear. It would provide new theoretical references for the study of anthocyanin synthesis regulation in pear.

Li Shuran, a doctoral student jointly trained by Shenyang Agricultural University and  IPCAAS, and Associate Researcher Ou Chunqing from IPCAAS, are co-first authors of this article. Researcher Jiang Shuling and Professor Li He are co-corresponding authors of this article. Researchers from the Egyptian National Research Center, Agricultural Research Center, Ain Shamm University, and King Abdulaziz University in Saudi Arabia also participated in this research work. This study was supported by projects such as the National Natural Science Foundation of China (32072531), the Science and Technology Innovation Program of CAAS (CAAS-ASTIP-2016-RIP), the National Key Research and Development Program (2021YFE0190700), and the Egyptian Science and Technology Innovation Fund (43093).

Link: https://doi.org/10.1016/j.jia.2024.11.005

By: Ou Chunqing

(ouchunqing@caas.cn)