Genome-wide identification and functional prediction of Phloem Protein 2 gene family in cassava (Manihot esculenta)

Phloem Protein 2 (PP2) regulates phloem-based defense, contributing to plant growth and stress tolerance. While PP2s are known to aid stress responses in cotton, rapeseed, and bamboo, their roles in cassava are less explored. This study identified fifteen PP2 gene family members in cassava, grouped into four distinct clusters based on maximum likelihood phylogenetic analysis. These genes typically contain two to three exons and one or two introns. The PP2 proteins harbor six conserved domains, including PP2, PP2 superfamily, F-box, F-box-like, F-box superfamily, and F-box-like superfamily, suggesting their involvement in stress response and regulatory functions. The conserved domain, motifs, and gene structures of PP2s aligned with their phylogenetic relationships. Furthermore, the MePP2 expression profiling revealed remarkably high transcript levels of Manes.18G077300, Manes.02G027400, Manes.08G018500, and Manes.09G061300 across all cassava tissues, indicating their potential role in overall growth and yield improvement. Although Manes.08G114900 and Manes.08G115000 were not inducible to root wounding, their transcripts highly accumulated in response to drought and cold stress exposure in the leaves, suggesting their role in shoot development and stress tolerance. The MePP2 genes also intricately interact with LIP4, ATLTP44, and GDSL, potentially contributing to growth and stress tolerance. This study lays a foundation for further studies to elucidate the putative function of PP2 genes in cassava.