Research Focus
Crop trait improvement using genetic engineering and genome editing
Plant tissue culture and transformation
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A major challenge that often impedes the use of genome editing in many plant species is the lack of efficient genetic transformation systems and the low efficiency of reagent delivery into plant cells. The Zhang lab focuses on developing efficient plant regeneration system as well as innovative genotype-independent delivery methods that bypass the time-consuming and laborious tissue culture process. ​​
Plant genome editing
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The CRISPR/Cas9 system is a powerful tool for targeted gene editing in many organisms including plants. Derived from a native adaptive immune system in eubacteria and archaea, the CRISPR/Cas system enables the alteration of DNA sequences in many organisms to achieve precise gene modifications. The most widely used Streptococcus pyogenes Cas9 (SpCas9) requires the 20-bp spacer sequence of a guide RNA (gRNA) to recognize a complementary target DNA site upstream of a protospacer adjacent motif (PAM) and generates a double-stranded break (DSB) near the target DSBs are repaired through either non-homologous end joining (NHEJ) or homology-directed recombination (HDR) resulting in small insertions/deletions (indels) or substitutions at the target region, respectively.
The Zhang lab is focused on developing advanced genome editing tools for broader applications in functional genetics and plant breeding. Our current project aims to develop tomato knockout mutants by disrupting candidate immunity-associated genes using CRISPR/Cas9 to test whether these mutations make a demonstrable contribution to plant immunity. The ultimate goal of the Zhang lab's research is to develop plants with enhanced disease resistance through precise genome editing techniques.
CRISPR/Cas9
Investigate the molecular basis of plant immunity against bacterial pathogens
Plants have evolved sophisticated surveillance mechanisms to rapidly recognize and respond to pathogen attacks. The first layer of plant immunity, referred as pattern-triggered immunity (PTI), is activated when plant cells detect microbe-associated molecular patterns (MAMPs) through transmembrane pattern recognition receptors (PRRs), such as Fls2 and Fls3. Successful pathogens deploy effectors into plant cells that interfere with PTI, leading to effector-triggered susceptibility (ETS). To defeat ETS, plants activate a more robust immune response, effector-triggered immunity (ETI), where nucleotide-binding leucine-rich repeat (NB-LRR or NLR) proteins directly or indirectly recognize a given effector, resulting in a hypersensitive cell death response (HR) and disease resistance.
The Zhang laboratory focuses on studying the molecular basis of bacterial infection processes and the plant immune system. Our model system is tomato speck disease, caused by the bacterial pathogen Pseudomonas syringae pv. tomato, an economically important disease that can significantly reduce the yield and marketability of tomato fruits. To address this, we employ a wide range of experimental approaches, integrating methods from molecular biology, genetics, biochemistry, bioinformatics, plant pathology, and plant biotechnology.​
Tomato speck disease caused by Pseudomonas syringae pv. tomato
The two-layered plant immune system: PTI & ETI
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