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| Common Broomrape, Orobanche minor Illustration: Catherine Hounslow-Webber From The Malevolent Designer: Why Nature's God is not Good © Catherine Hounslow-Webber. |
Good news for intelligent [sic] design advocates!
Researchers at Nagoya University, Japan, have worked out how parasitic plants have been modified to make it easier for them to parasitise other plants. They secrete an enzyme known as β-1,4-glucanase (GH9B3). They showed that the process of attaching the haustorium (the organ through which a parasitic plant extracts water and nutrients from its victim is very similar to the way a graft unites the tissues of the scion and the stock. The press release from Nagoya University explains:
Plant parasitism is a phenomenon by which the parasite plant latches onto and absorbs water and nutrients from a second host plant, with the help of a specialized organ called the "haustorium." Once the haustorium forms, specific enzymes then help in forming a connection between the tissues of the parasite and host plants, known as a "xylem bridge," which facilitates the transport of water and nutrients from the host to the parasite.
A similar mechanism is involved in the process of artificial stem grafting, during which, the cell walls of the two different plant tissues at the graft junction become thinner and compressed, a phenomenon made possible by specific cell wall modifying enzymes. Cell wall modification has also been implicated to play a role in parasitism in different lineages of parasitic plants.
Therefore, the research team, led by Dr Ken-ichi Kurotani of Nagoya University, hypothesized that similar genes and enzymes should be involved in the process of parasitism and cross-species grafting. "To investigate molecular events involved in cell-cell adhesion between P. japonicum and the host plant, we analyzed the transcriptome for P. japonicum-Arabidopsis parasitism and P. japonicum-Arabidopsis grafting," reports Dr Kurotani. When a gene in a cell is activated, it produces an RNA "transcript" that is then translated into an active protein, which is then used by the cell to perform various activities. A "transcriptome" is the complete set of RNA transcripts that the genome of an organism produces under various diverse conditions. The findings of their experiments are published in Nature's Communications Biology.
Comparison of the parasitism and graft transcriptomes revealed that genes associated with wound healing, cell division, DNA replication, and RNA synthesis were highly upregulated during both events, indicating active cell proliferation at both the haustorium and graft interface.
"What's more, we found an overlap between the transcriptome data from this study and that from grafting between Nicotiana and Arabidopsis, another angiosperm," reports Dr Michitaka Notaguchi, the co-corresponding author of the study. Glycosyl hydrolases are enzymes that specifically target the breakdown of cellulose, the primary component of plant cell walls. A β-1,4-glucanase identified in P. japonicum belongs to the glycosyl hydrolase 9B3 (GH9B3) family; an enzyme from the same family was recognized to be crucial for cell-cell adhesion in Nicotiana by Dr Notaguchi's group.
Further experiments showed that GH9B3-silenced P. japonicum could form the haustorium with Arabidopsis but could not form a functional xylem bridge, meaning that the P. japonicum β-1,4-glucanase is integral for the plant's parasitic activity. Further, high GH9B3 RNA transcript levels were observed during artificial grafting experiments, thereby proving that the enzyme plays an integral role in both parasitism and grafting mechanisms.
The team's findings were published, open access in Communications Biology:
Abstract
Tissue adhesion between plant species occurs both naturally and artificially. Parasitic plants establish intimate relationship with host plants by adhering tissues at roots or stems. Plant grafting, on the other hand, is a widely used technique in agriculture to adhere tissues of two stems. Here we found that the model Orobanchaceae parasitic plant Phtheirospermum japonicum can be grafted on to interfamily species. To understand molecular basis of tissue adhesion between distant plant species, we conducted comparative transcriptome analyses on both infection and grafting by P. japonicum on Arabidopsis. Despite different organs, we identified the shared gene expression profile, where cell proliferation- and cell wall modification-related genes are up-regulated. Among genes commonly induced in tissue adhesion between distant species, we showed a gene encoding a secreted type of β-1,4-glucanase plays an important role for plant parasitism. Our data provide insights into the molecular commonality between parasitism and grafting in plants.
Kurotani, Ken-ichi; Wakatake, Takanori; Ichihashi, Yasunori; Okayasu, Koji; Sawai, Yu; Ogawa, Satoshi; Cui, Songkui; Suzuki, Takamasa; Shirasu, Ken; Notaguchi, Michitaka
Host-parasite tissue adhesion by a secreted type of β-1,4-glucanase in the parasitic plant Phtheirospermum japonicum
Communications Biology; 3, 407 (2020). DOI:10.1038/s42003-020-01143-5
Copyright: © 2020 The authors, published by Springer Nature
Open access
Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0)
In intelligent [sic] design terms this ingenious design must be so that parasitic plants are better able to exploit their victims more easily - the same victims that the same putative designer designed in the first place. ID advocates are prohibited from ascribing a process such as this to either natural events not requiring supernatural interventions and intent, or to more than one designer, since it must comply with the Abrahamic notion of a single creative entity to make it conform to Christian, Muslim or Judaic holy books.
Unfortunately, this forces them to deny the only mechanism that doesn't make their favourite deity come across as malevolent and psychopathic in the uncaring and exploitative nature of many of its designs.
This and many other examples of the malevolence of any putative designer of nature is in my forthcoming, richly illustrated book, The Malevolent Designer: Why Nature's God is not Good, soon the be available in paperback and ebook for Kindle formats as a companion volume to my popular book, The Unintelligent Designer: Refuting the Intelligent Design Hoax.
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