The December 2020 Editor’s Pick
for MPMI is “Sec-Delivered
Effector 1 (SDE1) of ‘Candidatus
Liberibacter asiaticus’ Promotes Citrus Huanglongbing,”
in which Kelley Clark
and co-authors demonstrate the effect that the SDE1 protein from the citrus greening
(huanglongbing) pathogen can have on plants. Their results show that the effector
is an important virulence factor that induces premature senescence-like responses
in both Arabidopsis and citrus host plants.
Sec-Delivered Effector 1 (SDE1)
Liberibacter asiaticus’ Promotes Citrus Huanglongbing
Name: Kelley J. Clark
Postdoctoral researcher, University of Arkansas (located at USDA-ARS Salinas, CA).
Ph.D. degree in microbiology and plant pathology at the University of California,
Riverside, and B.S. degree in plant sciences at the University of Arizona.
Gardening, traveling to national parks, hiking, walking my cat.
Bio: Currently, I am a postdoctoral researcher for the University
of Arkansas, but stationed in Salinas, CA, at the USDA-ARS facilities. My research
project is on spinach downy mildew, and I am located in the Salinas Valley because
it is the “salad bowl of the world,” producing the majority of the leafy greens
we consume! The research recently published in MPMI is the final chapter of my Ph.D. thesis from
my time at UC Riverside under the supervision of Prof. Wenbo Ma. Our overarching goal was
to understand how an effector of Candidatus Liberibacter asiaticus contributes to huanglongbing
(HLB) disease progression. More specifically, for this publication we wanted to
understand how the effector SDE1 contributes to leaf yellowing in Arabidopsis and
how this relates to HLB yellowing symptoms in citrus.
project challenged me on many levels, both intellectually and emotionally, especially
as my passion for research progressed and I grew as a scientist. The HLB-associated
pathogen, Ca. L.
asiaticus, is obligate, which presents many obstacles, but also opportunities, for
novel research. During my Ph.D. studies, I was fortunate to learn several new techniques,
have access to state-of-the art technology, and collaborate with distinguished scientists.
For this project, we had access to SDE1-transgenic citrus, which would not have
been possible without help from our collaborators Prof. Nian Wang and Dr. Zhiqian Pang at the
University of Florida. Additionally, we implemented NanoString technology to directly
measure the transcript quantity of specific genes in citrus. Although this technology
is widely used in medical research, it holds tremendous potential for plant–microbe
interaction research, as well as other fields of study.
addition to gaining a technical skill set, I grew passionate about citriculture
from studying its history in Riverside, CA. When I moved to Riverside to pursue
my Ph.D. research, I volunteered at the California Citrus State Historic Park. The
park consists of more than 250 acres of citrus groves showcasing more than 80 different
citrus varieties and includes a museum highlighting the history of citrus in California.
Did you know that Riverside is home to the parent Navel orange tree planted by Eliza Tibbets
tree is still alive today,
and you can visit it on the corner of Magnolia and Arlington Streets, but due to
the threat of HLB, the tree is covered with a mesh tent to keep out the insect vector
that transmits Ca.
L. asiaticus. Volunteering at the park gave me the opportunity to immerse myself
in the rich culture of citrus and see others admire it is as well, which drove my
research efforts, since HLB continues to threaten not only the citrus industry,
but our connection to its past, present, and future.
look forward to working on more challenging and insightful projects in the future,
incorporating both the knowledge I gained from this research and the inspiration
I drew from learning about the agricultural history of a specific crops.