The Arabidopsis Tóxicos en Levadura (ATL) protein is a subfamily of the E3 ubiquitin ligases, which exists widely in plants and is extensively involved in plant growth and development. Although the ATL family has been identified in other species, such as Arabidopsis, Oryza sativa, and grapevine, few reports on pear ATL gene families have been reported. In this study, 92 PbrATL genes were identified and analyzed from the Pyrus breschneideri genome. Motif analysis and phylogenetic tree generation divided them into nine subgroups, and chromosome localization analysis showed that the 92 PbrATL genes were distributed in 16 of 17 pear chromosomes. Transcriptome data and quantitative real-time polymerase chain reaction (qRT-PCR) experiments demonstrated that PbrATL18, PbrATL41, and PbrATL88 were involved in both pear drought resistance and Colletotrichum fructicola infection. In addition, Arabidopsis thaliana overexpressing PbrATL18 showed greater resistance to drought stress than the wild type (WT), and PbrATL18-silenced pear seedlings showed greater sensitivity to drought and C. fructicola infection than the controls. PbrATL18 regulated plant resistance by regulating chitinase (CHI), phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities. This study provided a reference for further exploring the functions of the PbrATL gene in drought resistance and C. fructicola infection.

The mitogen-activated protein kinase (MAPK) cascade is crucial to plant growth, development, and stress responses. MAPK kinases (MAPKK) play a vital role in linking upstream MAPKK kinases (MAPKKK) with the downstream MAPK. Black spot is one of the most serious fungal diseases of pear which is an important part of the fruit industry in China. The MAPKK genes have been identified in many plants, however, none has been reported in pear (Pyrus bretschneideri). In order to explore whether MAPK gene of pear is related to black spot disease, we designed this experiment. The present study investigated eight putative PbrMAPKK genes obtained from the Chinese white pear genome. The phylogenetic analysis revealed that PbrMAPKK genes were divided into A, B, C, and D groups. These PbrMAPKK genes are randomly distributed on 7 out of 17 chromosomes and mainly originated from the whole-genome duplication (WGD) event. The expression analysis of PbrMAPKK genes in seven pear tissues and the leaves of susceptible and resistant varieties after Alternaria alternata infection by quantitative real-time PCR (qRT-PCR) identified seven candidate genes associated with resistance. Furthermore, virus-induced gene silencing (VIGS) indicated that PbrMAPKK6 gene enhanced resistance to pear black spot disease in pear.

N⁶-methylated adenine (m⁶A) is an emerging epigenetic marker in eukaryotic organisms that plays an important role in biological functions and in enriching genetic information. m⁶A exerts these functions via the dynamic interplay among m⁶A writers, erasers, and readers. However, little is known about the underlying mechanisms of m⁶A in plant growth and stress responses. Here, we identified 276 masked m⁶A regulators from nine Rosaceae species (Pyrus bretschneideri, Pyrus betulifolia, Pyrus communis, Malus domestica, Fragaria vesca, Prunus avium, Prunus mume, Prunus persica, and Rubus occidentalis). We classified and named these genes in more detail based on phylogenetic and synteny analysis. The expansion of m⁶A regulators in Maloideae was dated back to the recent whole-genome duplication (WGD) in Rosaceae. Based on the expression pattern analysis and gene structure analysis of m⁶A regulators, m⁶A was shown to be a significant factor in regulating plant development and resistance. In addition, PbrMTA1-silenced pear plants displayed significantly reduced drought tolerance and chlorophyll content, as well as increased electrolyte leakage and concentrations of malondialdehyde and H₂O₂.