TITLE:
Expression Profiles of psbA, ALS, EPSPS, and Other Chloroplastic Genes in Response to PSII-, ALS-, and EPSPS-Inhibitor Treatments in Kochia scoparia
AUTHORS:
Vijay K. Varanasi, Shahniyar Bayramov, P. V. Vara Prasad, Mithila Jugulam
KEYWORDS:
Kochia scoparia L. Schrad., C4, Herbicide Stress, Gene Expression, psbA, ALS, EPSPS, Photosynthesis, Rubisco, PPDK, CAB
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.3,
February
9,
2017
ABSTRACT: Kochia (Kochia
scoparia L. Schrad.), also known as tumbleweed, is an economically
important annual C4 broadleaf weed found throughout the US Great Plains.
Several herbicides with different modes of action are used in the management of
kochia. The effect of commonly used herbicides on the expression of their
target site(s) and photosynthetic/chloroplastic genes is poorly understood in
weed species, including kochia. The objective of this research was to characterize the expression profiles of
herbicide target-site genes, KspsbA, KsALS, and KsEPSPS upon treatment with PSII- (e.g. atrazine), ALS- (e.g.
chlorsulfuron), and EPSPS- (e.g. glyphosate)-inhibitors, respectively, in kochia.
Furthermore, the expression of genes involved in photosynthesis (e.g. KsRubisco, KsCAB, and KsPPDK) was also
determined in response to these herbicide treatments. KspsbA was strongly upregulated (>200-fold) 24 h after atrazine
treatment. Transcript levels of the KsALS or KsEPSPS genes were 7 and
3-fold higher 24 h after chlorsulfuron or glyphosate treatment, respectively. KsRubisco, a Calvin cycle gene important
for CO2 fixation, was upregulated 7 and 2.6-fold 8 and 24 h after
glyphosate and chlorsulfuron treatments, whereas it downregulated 8 and 24 h
after atrazine treatment. The transcript levels of KsPPDK remained unchanged after glyphosate treatment but increased
1.8-fold and decreased 2-fold at 24 h after chlorsulfuron and atrazine
treatments, respectively. KsCAB remained unchanged after chlorsulfuron treatment, but was downregulated after
glyphosate and atrazine treatments. The results show that herbicide treatments
not only affect the respective target-site gene expression, but also influence
the genes involved in the critical photosynthetic pathway.