A Novel Effector Protein, MJ-NULG1a, Targeted to Giant Cell Nuclei Plays a Role inMeloidogyne javanicaParasitism

Abstract

Secretory effector proteins expressed within the esophageal glands of root-knot nematodes (Meloidogyne spp.) are thought to play key roles in nematode invasion of host roots and in formation of feeding sites necessary for nematodes to complete their life cycle. In this study, a novel effector protein gene designated as Mj-nulg1a, which is expressed specifically within the dorsal gland of Meloidogyne javanica, was isolated through suppression subtractive hybridization. Southern blotting and BLAST search analyses showed that Mj-nulg1a is unique for Meloidogyne spp. A real-time reverse-transcriptase polymerase chain reaction assay showed that expression of Mj-nulg1a was upregulated in parasitic second-stage juveniles and declined in later parasitic stages. MJ-NULG1a contains two putative nuclear localization signals and, consistently, in planta immunolocalization analysis showed that MJ-NULG1a was localized in the nuclei of giant cells during nematode parasitism. In planta RNA interference targeting Mj-nulg1a suppressed the expression of Mj-nulg1a in nematodes and attenuated parasitism ability of M. javanica. In contrast, transgenic Arabidopsis expressing Mj-nulg1a became more susceptible to M. javanica infection than wild-type control plants. These results depict a novel nematode effector that is targeted to giant cell nuclei and plays a critical role in M. javanica parasitism.

Gall-forming root-knot nematodes hijack key plant cellular functions to induce multinucleate and hypertrophied feeding cells

“…Manipulation of the plant's cell cycle, gene expression, and immunity clearly involves targeting of the host nucleus by secreted effectors. Recently, the first discovery was made of RKN effectors that are effectively delivered to GC nuclei and function in the early stages of colonization (Jaouannet et al, 2012;Lin et al, 2013). The…”

“…Using also an immunolocalization approach, a 274 aa pioneer of M. javanica with two NLS, MjNULG1a, was shown to localise in GC nuclei (Lin et al, 2013). The identification of the host cell targets of these proteins is underway and should shed light on their functions.…”

Plant parasitic nematode effectors target host defense and nuclear functions to establish feeding cells

“…Recently, immunolocalization approaches have shown two RKN effectors to be effectively delivered to giant cell nuclei (Jaouannet et al, 2012; Lin et al, 2013). Immunostainings demonstrate MiEFF1 is produced in the dorsal esophageal gland of the nematode and is secreted through the stylet into the giant cells, in which it is transported into the nuclei ( Figures 1F,G ; Jaouannet et al, 2012).…”

“…Similarly, M. javanica MjNULG1a is a 274 aa protein of unknown function with two predicted NLS localizing in FC nuclei. Transgenic plants overproducing MjNULG1a are more sensitive to RKN, and RNAi studies in planta have provided evidence of a role for this protein in nematode parasitism (Lin et al, 2013). Both MiEFF1 and MjNULG1a seem to be specific to early steps in parasitism, but it remains unclear whether these effectors are involved in giant cell formation.…”

Mining Novel Effector Proteins from the Esophageal Gland Cells ofMeloidogyne incognita

“…show homology to chorismate mutases and have been shown to alter plant development when expressed in planta (Bekal S, 2003; Doyle and Lambert, 2003). Yet another effector protein, Mj-NULG , was recently isolated from the closely related species Meloidogyne javanica and was shown to be specifically up-regulated during feeding site development and to localize to the nucleus of the giant-cells, where it is assumed to play a role in facilitating nematode parasitism (Lin et al, 2012). Similarly, the secreted M. incognita effector, Mi-EFF1, was shown to localize to the plant nucleus where it has the potential to manipulate host transcriptional machinery (Jaouannet et al, 2012).…”