Genome-wide identification, expression analysis, and functional verification of the JMJ (Jumonji) histone demethylase gene family in pear ( Pyrus bretchneideri )

Jumonji (JMJ) genes play major roles in the modulation of chromatin at certain stages of plant development such as flowering, development of androecium and gynoecium, circadian regulation, and brassinosteroid signalling. However, the information on this gene family in pear ( Pyrus bretschneideri ) is limited. In this study, 19 PbrJMJ genes were identified and divided into five groups. Their gene structures and conserved domains shared a resemblance within the same groups. 18 PbrJMJ genes were presented on 8 of the 17 chromosomes in the pear. In the expansion of the PbrJMJ genes family, the whole-genome duplication event played a critical role, and the evolution of the PbrJMJ family was mainly affected by purification selection pressure. Gene expression analysis revealed that PbrJMJ genes were distributed in various tissues of P. bretschneideri . PbrJMJ 14 and PbrJMJ 29 were highly expressed in the pollen. Inhibition of PbrJMJ 14 and PbrJMJ 29 expression resulted in reduced pollen tube length, suggesting that they play a role in regulating pollen tube growth. In summary, these results provide evolutionary insight into PbrJMJ genes and lay a foundation for further analysis of their functions.