Starch content changes and metabolism-related gene regulation of Chinese cabbage synergistically induced by Plasmodiophora brassicae infection

Abstract

Clubroot is one of the major diseases adversely affecting Chinese cabbage (Brassica rapa) yield and quality. To precisely characterize the Plasmodiophora brassicae infection on Chinese cabbage, we developed a dual fluorescent staining method for simultaneously examining the pathogen, cell structures, and starch grains. The number of starch (amylopectin) grains increased in B. rapa roots infected by P. brassicae, especially from 14 to 21 days after inoculation. Therefore, the expression levels of 38 core starch metabolism genes were investigated by quantitative real-time PCR. Most genes related to starch synthesis were up-regulated at seven days after the P. brassicae inoculation, whereas the expression levels of the starch degradation-related genes increased at 14 days after the inoculation. Then genes encoding the core enzymes involved in starch metabolism were investigated by assessing their chromosomal distributions, structures, duplication events, and synteny among Brassica species. Genome comparisons indicated that 38 non-redundant genes belonging to six core gene families related to starch metabolism are highly conserved among Arabidopsis thaliana, B. rapa, Brassica nigra, and Brassica oleracea. Genome sequencing projects have revealed that P. brassicae obtained host nutrients by manipulating plant metabolism. Starch may serve as a carbon source for P. brassicae colonization as indicated by the histological observation and transcriptomic analysis. Results of this study may elucidate the evolution and expression of core starch metabolism genes and provide researchers with novel insights into the pathogenesis of clubroot in B. rapa.

Phagocytosis underpins the biotrophic lifestyle of intracellular parasites in the class Phytomyxea (Rhizaria)

“…However, it is known that host manipulation by P. brassicae , beside inducing mitosis and cellular expansion in the host (Olszak et al , 2019); generates a strong physiological sink, driving photosynthates to the infected host cells (Malinowski et al , 2019). Those photosynthates accumulate as starch in amyloplasts, which are significantly more abundant in the infected root cells of brassicas (Ma et al , 2022) where they appear to be superficially “plugged” into the plasmodium surface, reminding of a process of semi-extracellular phagocytosis (named “pomacytosis”, Kamennaya et al , 2018). Previous studies highlighted an upregulation of the plastidial MEX1 maltose transporter in infected roots, involved in the export of maltose outside the plastid after starch degradation (Badstöber et al , 2020, Supplementary Figure 5).…”

“…During that time sporogenic plasmodia induce hypertrophy of the infected cells which, coupled with induced hyperplasia of the tissue, leads to the formation of galls in the host (Murúa et al, 2017;Olszak et al, 2019). Manipulation of brassicaceae hosts by P. brassicae induces hypertrophied infected cells to act as physiological sinks, driving photosynthates from the aerial parts of the plant (Malinowski et al, 2019) and inducing their accumulation as starch grains in the root (Ma et al, 2022). How Phytomyxea feed on their host has never been clearly elucidated and even the trophic mode of the model phytomyxean P. brassicae is still debated (Bulman & Neuhauser, 2017).…”

Auxin participates in regulating the leaf curl development of Wucai (Brassica campestris L.)

“…The specimens were cut into 8–10 μm sections with a microtome (MICROM HM340E), dewaxed with xylene, stained with Safranin fast green counterstain, sealed with neutral resin, and observed (three biological replicates with one leaf from an individual plant per replicate) under a microscope (ZEISS SIP No. MIC01191, Germany; Ma et al, 2022; Qiu et al, 2019). Cell tense ratio (CTR) = sponge parenchyma thickness (ST)/leaf thickness (LT). Spongy ratio (SR) = palisade parenchyma thickness (PT)/LT. P/S = palisade tissue/sponge tissue. …”

“…The specimens were cut into 8-10 μm sections with a microtome (MICROM HM340E), dewaxed with xylene, stained with Safranin fast green counterstain, sealed with neutral resin, and observed (three biological replicates with one leaf from an individual plant per replicate) under a microscope (ZEISS SIP No. MIC01191, Germany; Ma et al, 2022;Qiu et al, 2019).…”

Application of the NanoString nCounter System as an Alternative Method to Investigate Molecular Mechanisms Involved in Host Plant Responses to Plasmodiophora brassicae

“…For example, qPCR was used to study the Mitogen-activated Protein Kinase ( MPK ) and MPK kinase gene families [ 18 ], the Myrosinase and Myrosinase-Binding Protein-like gene families [ 19 ], and the chitinase [ 20 ] and SWEET gene families [ 21 ]. Auxin signaling [ 22 ], cytokinin signaling [ 23 ], starch metabolism [ 24 ], and hormone signaling and phenylpropanoid-related genes [ 25 ] have also been evaluated by qPCR. However, as the scale of gene expression studies increases, with more targeted genes and larger sample sizes (e.g., cultivars with different levels of susceptibility, different tissues, and different infection stages), performing qPCR can be time-consuming, laborious, and less cost-effective.…”