The August 2020 Editor’s Pick for MPMI is, “Dual Role of Auxin in Regulating Plant Defense and Bacterial Virulence
Gene Expression During Pseudomonas
syringae PtoDC3000 Pathogenesis,” in which Arnaud Djami Tchatchou and co-authors show how plant hormones like auxin are
involved in disease resistance. Their results show that auxin signaling in the host
affects salicylic acid synthesis and can lead to susceptibility. They also found
that not only does auxin suppress host defense, but that it can also modulate virulence
gene expression in bacteria (Pst DC3000).
Dual Role of Auxin
in Regulating Plant Defense and Bacterial Virulence Gene Expression during Pseudomonas syringae PtoDC3000 Pathogenesis
Name: Arnaud Thierry Djami Tchatchou
Current Position:
Research scientist at Washington University in St. Louis, MO, USA.
Education: B.S. and M.S. degrees in biochemistry from the University of Yaounde
I, Cameroon, and Ph.D. degree in molecular biology from the University of the Witwatersrand,
South Africa.
Non-scientific
Interests: Cooking, bible study, having fun with
my family.
Brief-bio: I was born in a small village, Ndoungue, in Cameroon and raised up
by my grandparents, who were famers and hunters. Each time my grandfather brought
an animal home for food I was curious to see what was inside the stomach and the
head. As a primary- and high-school student
I was fascinated by biology and learning about the natural world and the ways in
which organisms interact with their environment, which were more real to me than
mathematics, literature, etc.... As I was growing up with my grandparents, we cultivated the ground manually to sow
cassava, sweetpotatoes, maize (see photo), and many vegetable crops. This is how my passion for
plants originated. Seeing my grandparents struggle with plant diseases in those
days, which sometimes resulted in severe losses in agricultural yield, I was curious to know why our crops couldn’t
defend themselves against those diseases. These struggles and difficulties faced
by my grandparents became the motivation that led me to study and seek to understand
how plants defend themselves against pathogen attacks. Since then I have been fascinated by the field of
plant biology and ways to address issues of global importance, such as improving
agricultural productivity and ensuring sustainable food security. As a graduate
student and post-doctorate, I have sought to understand the molecular basis of plant
disease resistance using a wide array of approaches, including biochemistry and
molecular biology.
Throughout my scientific career I have used various organisms (Colletotrichum gloeosporioides, Colletotrichum sublineolum, Pectobacterium
carotovorum, and Pseudomonas syringae),
as well as some
defense priming agents (isonitrosoacetophenone, hexanoic acid, azelaic acid,
and bacterial lipopolysaccharide),
to study their interactions with both model plants (Arabidopsis thaliana
and Nicotiana tabacum) and crop species
(avocado, sorghum, tomato, and chili pepper). I have identified and characterized various defense-
and virulence-related genes to uncover
the mechanisms of plant disease resistance and virulence. In Prof. Barbara Kunkel’s group
at Washington University in St. Louis, my research focus is to investigate the roles
of the plant hormone auxin (indole acetic acid [IAA]) during pathogenesis of P. syringae DC3000 on A. thaliana. I found that
P. syringae uses IAA in at least two different
ways to promote virulence and disease: as a plant hormone to suppress plant defenses
and as a microbial signaling molecule to regulate virulence gene expression (the
subject of the paper we just published in MPMI). Currently, my research focus is to translate the scientific discoveries about
auxin that we made using Arabidopsis to two agriculturally important plants, tomato and cassava, using
Xanthomonas campestris, an economically important pathogen. This study
will provide new insights into mechanisms regulating Xanthomonas–host interactions that can be exploited
to develop new strategies for protection of tomato and cassava against devastating
plant diseases caused by X. campestris.
During the years I spent here I have
learned a lot about working with transgenic plants and gained more knowledge in
microbiology with excellent mentorship from Prof. Kunkel, which I think will boost
my research career.