The Phtheirospermum japonicum isopentenyltransferase PjIPT1a regulates host cytokinin responses in Arabidopsis

Abstract

 The hemiparasitic plant Phtheirospermum japonicum is a nutritional specialist that supplements its nutrient requirements by parasitizing other plants through haustoria. During parasitism, the Phtheirospermum haustorium transfers hypertrophy-inducing cytokinins (CKs) to the infected host root. The CK biosynthesis genes required for haustorium-derived CKs and the induction of hypertrophy are still unknown.  We searched for haustorium-expressed isopentenyltransferases (IPTs) that catalyse the first step of CK biosynthesis, confirmed the specific expression by in vivo imaging of a promoterreporter, and further analysed the subcellular localization, the enzymatic function, and contribution to inducing hypertrophy by studying CRISPR-Cas9 induced Phtheirospermum mutants.  PjIPT1a was expressed in intrusive cells of the haustorium close to the host vasculature. PjIPT1a and its closest homolog PjIPT1b located to the cytosol and showed isopentenyltransferases activity in vitro with differences in substrate specificity. Mutating PjIPT1a abolished parasite-induced CK responses in the host. A homolog of PjIPT1a was also identified in the related weed Striga hermonthica.  With PjIPT1a, we identified the IPT enzyme that induces CK responses in Phtheirospermum japonicum-infected Arabidopsis roots. We propose that PjIPT1a exemplifies how parasitismrelated functions evolve through gene duplications and neofunctionalization.

Strigolactones are chemoattractants for host tropism in Orobanchaceae parasitic plants

“…With the advent of genetic tools, including ethyl methyl sulfonate-driven mutagenesis and Agrobacterium rhizogenes -mediated root transformation 10 , 15 , 16 , P. japonicum has been used as a model Orobanchaceae species to investigate parasitism. These studies have revealed the molecular mechanisms regulating haustorium development, vasculature connection and exchange of molecules 12 – 14 , 16 – 20 . As a facultative parasite, P. japonicum does not require host-derived stimulants, such as SLs, for germination.…”

Investigating Host and Parasitic Plant Interaction by Tissue-Specific Gene Analyses on Tomato and Cuscuta campestris Interface at Three Haustorial Developmental Stages

“…This hypertrophy phenotype enlarged the width of xylem tissues in the host root right above haustoria attachment sites, which could help the parasites uptake more water and nutrients from the host. The induction of cytokinin and ethylene might be one reason for the hypertrophy phenotype ( Spallek et al, 2017 ; Mignolli et al, 2020 ; Greifenhagen et al, 2021 ). However, the detailed mechanism underlying parasitic plant-induced hypertrophy remains unknown.…”

Overexpression of ZmIPT2 gene delays leaf senescence and improves grain yield in maize

“…An ATP/ADP-PpIPTs study found that the overexpression of PpIPT1 , PpIPT3 , PpIPT5 , and PpIPT7 genes in Arabidopsis can increase cytokinin content in transgenic plants and improve salt resistance ( Li et al, 2018 ). CRISPR/Cas9 targeted gene knockout Phtheirospermum japonicum (Pj)IPT1a inhibits parasite induced CTK response in host, revealing the important role of PjIPT1a in Arabidopsis phloem-induced CTK response ( Greifenhagen et al, 2021 ). In the transgenic Camellia sinensis containing IPT5 , the 3’ UTR variant 2 (3AS2) was found to be the main transcript which participated in the regulation of tea axillary bud germination and shoot branching, providing gene resources for improving the plant type of woody plants ( Zhang et al, 2021 ).…”