The transcription factor PbrMYB24 regulates lignin and cellulose biosynthesis in stone cells of pear fruits.

Lignified stone cell content is a key factor used to evaluate fruit quality, influencing the economic value of pear (Pyrus pyrifolia) fruits. However, our understanding of the regulatory networks of stone cell formation is limited due to the complex secondary metabolic pathway. In this study, we used a combination of co-expression network analysis, gene expression profiles, and transcriptome analysis in different pear cultivars with varied stone cell content to identify a hub MYB gene, PbrMYB24. The relative expression of PbrMYB24 in fruit flesh was significantly correlated with the contents of stone cells, lignin, and cellulose. We then verified the function of PbrMYB24 in regulating lignin and cellulose formation via genetic transformation in homologous and heterologous systems. We constructed a high-efficiency verification system for lignin and cellulose biosynthesis genes in pear callus. PbrMYB24 transcriptionally activated multiple target genes involved in stone cell formation. On the one hand, PbrMYB24 activated the transcription of lignin and cellulose biosynthesis genes by binding to different cis-elements [AC-I (ACCTACC) element, AC-II (ACCAACC) element and MYB-binding sites (MBS)]. On the other hand, PbrMYB24 bound directly to the promoters of PbrMYB169 and NAC STONE CELL PROMOTING FACTOR (PbrNSC), activating the gene expression. Moreover, both PbrMYB169 and PbrNSC activated the promoter of PbrMYB24, enhancing gene expression. This study improves our understanding of lignin and cellulose synthesis regulation in pear fruits through identifying a regulator and establishing a regulatory network. This knowledge will be useful for reducing the stone cell content in pears via molecular breeding.

Analysis of Farmland Abandonment and Government Supervision Traps in China.

Farmland abandonment has become relatively common in rural China. In the context of food security, the Chinese government has introduced policies for farmland abandonment supervision, but the effect of these policies has proven to be marginal. By constructing an evolutionary game model, our research explores the evolutionary logic during the supervision of farmland abandonment by governments and rural households. The results indicate that low food yield and high opportunity costs are the leading causes of farmland abandonment. The probable punishment administered by the central government for dereliction is a major motivation for the local government to practice farmland abandonment supervision. The low supervision avoidance cost for rural households leads local governments and households to form collaborations to jointly cope with central government supervision. When this occurs, local governments' supervision of farmland abandonment falls into a trap, as it leads to continued supervision practices that are costly and ineffective. Food security risk comes from the contradictory population and land resources demands. To improve food security while managing these contradictory demands, it is both necessary and feasible for the government to control population growth and focus on farmland protection, whereas it is unnecessary and unfeasible for the government to supervise whether or not farmland should be abandoned.