My post-doctoral research from 1995 to 1999 included searching for, sequencing and characterizing genes of chloroplast genomes of holoparasitic plants (plants that cannot obtain energy from the sun and must steal it from other plants). I am preparing to give a seminar tomorrow on the topic of parasitic plants. So much has been learned since I last worked on these plants and it’s been fascinating to catch of on recent research.
While searching for the latest news on parasitic plants and stumbled onto an archived post from a long-since defunct e-mail list serve. For you youngsters out there this was sort of the original social media. I was part of a group that had conversations through our computers via emails. Any email sent to the list was disseminated to all the other members of the group any of which could respond. This email list was hosted by ASA (American Scientific Affiliation) and is one of three lists that I was a member of that sometime discussed questions of origins and the Christian faith.
The “post” that I stumbled upon was written, to my great surprise, by none other than myself. In fact, it was my very first attempt to add to the conversation and thus was my first time speaking out on the internet rather than in-person contacts at church and school. That was 24 years ago! This post is partially responsible for setting me on the path to eventually creating this blog.
I have copied that entire post below with some formatting changes which were not possible with the email technology of the day. I post this here for a couple of reasons:
- As an example of my own history of thought on the topic of origins. I think what I say here hold up better than I would have expected but there are many angles to this topic that never would have occurred to me in the 1990s. I’m not even really sure where I was going in that last section under “EC” (which was a very young term at the time), which shows how much I hadn’t thought about the nuances of this topic back then.
- The question of parasitic plants is still an valuable one to think about and after my seminar tomorrow I plan to make a couple of videos that will dig much further into parasitic plant biology and the questions I ask in this post. Does anything we have learned about the biology of parasitic plants in the last 20 years cause me to think differently? Yes and no, but I will get to that. As I suggested above, I would have written this post quite differently if I were to do it again.
- Many of you will recognize the name Glenn Morton as having written the “previous message.” I want to recognize Glenn’s work at this time as having some considerable influence on me as he so patiently and diligently wrote on so many issues of creationism.
Without further ado, below is my first post to the ASA e-mail list on Monday July 22, 1996.
Robert Joel Duff (email@example.com)
Mon, 22 Jul 1996 23:34:49 -0500
- Messages sorted by: [ date ][ thread ][ subject ][ author ]
- Next message: Bill Hamilton: “Re: Parasitic plants, death, and the fall”
- Previous message: Glenn Morton: “Re: After their kind”
- Next in thread: Bill Hamilton: “Re: Parasitic plants, death, and the fall”
I’ve been reading and listening for four months now and after many distractions I’ve finally gotten around to getting some thoughts together. I am a postdoctoral student in Plant Biology at Southern Illinois University and work on the molecular biology of chloroplast DNA of parasitic plants. I have had a long history of dealings in the creation/evolution arena from my days at Calvin college as an undergraduate to graduate studies at the University of Tennessee. I thought I had run across every shade of creationists that there was until I started reading some archived stuff from this group.
Upon sifting through the archives I came upon a post of Terry Gray in which he threw out a question regarding parasitic associations involving animal situations if I remember right. It didn’t seem to pick up much of a response but it is a topic that I have found particularly stimulating and has aroused some interest among some of my YEC friends. In fact, it is a question posed to me by a YEC that revitalized my interest in the whole C/E controversy. Essentially the question put to me (without even realizing my own thoughts on evolution) was:
“What did parasitic plants do before the fall!?”
The question clearly implied that the holoparasitic plants that I study (plants that are totally incapable of photosynthesizing and rely totally on a host plant from which they derive both water, minerals, and metabolites) could not have existed with the life-history characteristics they now possess before the fall when all of creation was “good.” The question caught me off guard and I realized that I was ill prepared to defend any answer that I might be tempted to give. Thus the renewed interest into delving more heavily into the recent literature, discussions at church, this group, etc…
Parasitic plants reveal a very interesting molecular evolutionary trend difficult to account for in both the YEC camp and I believe even for most PCs (I confess to having a limited ability of defining the latter term and so may not be justified in this claim). Classic studies of Epifagus (Indian pipe) a holoparasitic (white) plant in the late 80’s (refs on request) revealed that they had lost more than one third of their chloroplast DNA relative to other green plants. The cpDNA is a remarkable “conserved” molecule in green plants consisting of ca. 120 genes in almost the same order and having extremely high sequence similarity (relative to nuclear genes) among all land plants (mosses to flowering plants).
In the case of Epifagus the cpDNA genome has lost major parts of the cpDNA most of which contained genes for photosynthetic capability although retaining some photosynthetic genes. Since this time several other presumably unrelated holoparasites have been looked at and they also have lost significant portions of their genome and all have lost genes that have something to do with photosynthesis. Significantly this loss of genes appears to be stochastic as the specific genes lost in each case are not the same. In several instances in the family Orobanchaceae, member species have lost the rbcL gene (the one that produces the enzyme the incorporates CO2 into sugars and is considered on of the most important enzymes on earth) completely, or just a portion of the gene, or none of it at all.
Members of this family range from normal green plants to partially parasitic plants (like mistletoes) to holoparasites. Only the holoparasites exhibit reduced cpDNA genomes or loss of functionality of particular genes in the chloroplast. The evolutionary explanation for this trend in cpDNA genomes is that hemiparasites (partially parasitic plants that still photosynthesize be get water and nutrients from the host) still place high selectional pressure on maintaining the genome organization and genes of the chloroplast because they still need to do photosynthesis for survival. The holoparasites on the other hand do not need the photosynthetic apparatus and so are discarding (differently in each lineage) the unneeded parts over time. It is important to point out that many of these parasitic plants maintain many photosynthetic genes that based on sequence analysis would work perfectly in a normal green plant. The question I posed down the line in conversation as a response to the question “what did parasitic plants do before the fall?” (because they weren’t parasitic then) was “What are plants doing with so many genes they don’t use?
Several hypotheses present themselves from several perspectives:
I: YEC perspective:
A: Parasitic plants were not around before the fall
They were green plants at the time which were affected by sin and parasitism was the result (either an instantaneous “creation” or they diverged from regular green plants but are still “of the same kind”) and thus had a normal cpDNA genome and has since then (6000- 10000years) been losing parts of the genome. This gradual loss idea was the response that was given to me at the time and it sounds reasonable to the untrained but would go against all knowledge of the rates of mutation in cpDNA.
An added complication to both the “special creation” or “gradual divergence” theories is that many holoparasitic plants require very specific (species) hosts and so had to get through the flood together somehow.
**An additional note – Members of the Orobanchaceae and some other holoparasites (Cuscuta – dodder) have obvious affiliation to other green plants upon morphological and molecular analyses and so the level of divergence in their genome is at the level of structural change and not really seen in actual sequence divergence but the plants I work on (Rafflesiaceae, Hydnoraceae, and Balanophoraceae) are so highly divergent from all other flowering plants that their relationships to other plants even at the Subclass level is of much dispute and interestingly gene sequences of these show that they have radically divergent genomes both on the structural and sequence level. A cpDNA genome from Rafflesia (the worlds largest flower) has yet to even be identified and looks to possibly be completely absent thus setting up a nice reductionist series from green plant to hemiparasite to recent holoparasites to holoparasites with complete loss of genomes. Although little fossil information is available, those fossils as well as sequence analyses of nuclear genes support the Rafflesiaceae as being extremely divergent from other plants and thus presumably has been a holoparasite for a longer time accounting for the increased portions of the genome lost.
If the above is due to gradual change since fall why the highly contrasted cpDNA types? If special creation then why have photosynthetic genes at the start at all if they were never meant to do photosynthesis?
B: There were parasitic plants in the Garden of Eden.
Death only referred to animals and not to plants and therefore plants death and even use of one plant by another is not prohibited. Surely plants were “dying” as Adam and Eve were chomping away.
1. In this case why did God create “from nothing” parasitic plants with genes they never used and presumably never will. Responses I’ve gotten here are “maybe we just don’t know what those genes do, we haven’t studied them enough, they might do something else in these parasitic plants.”
2. A second problem is that many of the same observations with respect to divergence rates among parasitic and non-parasitic animals show similar pattern to those of plant parasites. The same questions about animals could be asked as I am raising with plants with the added complication to the YEC that they certainly couldn’t be parasitic before the fall. What is raised in my mind is a question that I should think would trouble the YEC: that no easy distinction can be made between the plant and animal world that would allow one to say that death is all right in one situation but not alright in another.
II: EC Perspective
Parasitic plants are the result of an evolutionary process. This would seem to the most obvious option and is certainly attractive to me but does raise one hairy point regarding this theme of “death” with me I would appreciate enlightenment on. With respect to mans mortality there would be two options:
A: Man created immortal
Reading archived material with respect to the origins of man it seems that some are willing to allow for the immortality of man upon his creation (by whatever means) and at the same time say animals could die and that then sin brought “death” to Adam. I think that to be consistent one would have to say that going from a state of immortality, while at the same time having a fleshly body and then entering into a condition allowing death constitutes a fundamental biological change which is so profound it must be one of the real “mysteries” that we cannot understand.
Why, if sin can enact such a fundamental change in the way matter and energy works, cannot it be used to say that all of nature could have been fundamentally changed in the same way. Given this argument the following argument (of YEC connection) seems valid: that we cannot extrapolate back before the fall because everything in our experience has been changed in such a way that we cannot even imagine what it was like before. There have been numerous reasons discussed in this newsgroup why the last statement isn’t terrible desirable from both a “natural” and theological view.
B: Man created mortal
If man was created mortal (either uniquely or by evolution or variations thereof) then there doesn’t seem to be the problem presented in A except of course possible theological problems which I would like to have some discussion of because it is here that I think some real analysis it still needed for progress to be made in my mind. I would be interested in anyone who could point me to passages that are significant to this question. Much of the discussion of late would place many under this category but I am interested in what the potential pitfalls may be that I have not thought of and what needs further discussion.
III: Other scenarios that would fit under the umbrella of Gap theories, Day-age theories etc could also be expounded upon and I would like to hear about.
Postdoctoral Research Associate
Southern Illinois University
Carbondale IL 62901-6509
firstname.lastname@example.org (Note: no longer an active account)