The evolution of pectate lyase-like genes across land plants, and their roles in haustorium formation in parasitic plants

Abstract

Parasitic plants in the Orobanchaceae family are noxious agricultural pests that severely impact crops worldwide. These plants acquire water and nutrients from their hosts through a specialized organ called the haustorium. A critical process in the formation and function of the haustorium involves cell wall modification. In this study, we identified and analyzed the evolutionary relationships of pectate lyase-like (PLL) genes in parasitic plants and other major land plant lineages. One particular PLL gene, denoted as PLL1 in parasitic Orobanchaceae, which our previous research identified as a potential key parasitism gene, belongs to the largest sub-clade of this gene family. To explore the role of PLL1 gene in parasitic Orobanchaceae further, we manipulated its transcript abundance during haustorium development in Triphysaria versicolor, a model species in parasitic Orobanchaceae, using both direct transformation of the parasite and host-induced-gene-silencing (HIGS). For HIGS, we generated transgenic hosts (Medicago truncatula and Arabidopsis thaliana) carrying hairpin RNAs targeting the PLL gene in T. versicolor. Our results demonstrated that both methods effectively reduced the PLL1 expression in the haustorium of T. versicolor, leading to an increase in poorly adhered parasites. These findings highlight PLL1's crucial role in haustorium development in Orobanchaceae and may inform novel strategies towards parasitic weed management.