Baker Lab Research on Plant Innate Immunity

Our research focuses on understanding molecular-genetic mechanisms of plant innate immunity. We are investigating the structure, function and evolution of host genes for pathogen disease resistance. Our experimental system includes viral, bacterial and oomycete plant pathogens and their Solanaceae plant hosts. We anticipate that our studies will lead to new environmentally benign strategies for durable, broad-spectrum disease resistant crops.

Tobacco mosaic virus (TMV) triggers the N (Necrotic) resistance gene-mediated hypersensitive response (HR, brown lesions).

MicroRNA regulation of plant innate immune receptors

Plant innate immunity depends on recognition of pathogen effectors and triggering of host defenses. Plant resistance (R)-genes encode a major class of innate immune receptors. Plant microRNAs (miRNAs) and small interfering RNAs (siRNAs) guide gene silencing and play essential regulatory roles in development, genome function and host defense. We discovered novel miRNA families whose members silence R-genes including those encoding resistance to major pathogens of Solanaceae crops.

The SoMart webserver for plant miRNA and siRNA analysis

We designed the SoMart webserver with a suite of bioinformatic tools and sequence databases for discovery and analyses of miRNAs and siRNAs that regulate plant genes of interest.

The evolution of resistance genes in multi-protein plant resistance systems

Fast and slow evolving R-genes
R-gene evolution is thought to be facilitated by the formation of R-gene clusters, which permit sequence exchanges via recombinatorial mispairing and generate high haplotypic diversity. This pattern of evolution may also generate diversity at other loci that contribute to the R-complex.

NPK1, an MEKK1-like Mitogen-Activated Protein Kinase Kinase Kinase, Regulated Innate Immunity and Development in Plants

(Hailing Jin, UC Berkeley) The active defense of plants against pathogens often includes rapid and localized cell death known as hypersensitive response (HR). Protein phosphorylation and dephosphorylation are implicated in this event based on studies using protein kinase and phosphatase inhibitors. Recent transient gain-of-function studies demonstrated that the activation of salicylic acid-induced protein kinase (SIPK) and wounding-induced protein kinase (WIPK), two tobacco mitogen-activated protein kinases (MAPKs) by their upstream MAPK kinase (MAPKK), NtMEK2 leads to HR-like cell death.

Function of a Mitogen Activated Protein Kinase Pathway in N-gene Mediated Resistance in Tobacco

(Hailing Jin, UC Berkeley) The active defense of plants against pathogens often includes rapid and localized cell death known as hypersensitive response (HR). Protein phosphorylation and dephosphorylation are implicated in this event based on studies using protein kinase and phosphatase inhibitors.

Interaction Between Two Mitogen-Activated Protein Kinases during Tobacco Defense Singaling

(Hailing Jin, UC Berkeley) Plant mitogen-activated protein kinases (MAPKs) represented by tobacco wounding-induced protein kinase (WIPK) have unique regulation at the level of transcription in response to stresses. By using transcriptional and translational inhibitors, it has been shown previously that WIPK gene expression and de novo protein synthesis are requires for the high-level activity of WIPK in cells treated with elicitins from Phytophthora spp.

Genetic dissection of N mediated signal transduction in tomato

(Amy deHart, University of California, Berkeley) We are interested in isolating components on the N-mediated signal transduction pathway. Our approach is to isolate and characterize N gene suppressor mutants. We anticipate that this work will lead to a better understanding of the molecular mechanisms of plant disease resistance.The N gene confers a temperature sensitive hypersensitive response to tobacco mosaic virus (TMV) and effectively restricts TMV to sites of inoculation in transgenic tomato, as it does in tobacco (Whitham et al, 1996).

Identification of components of the N signal transduction pathway using the yeast two-hybrid system

(Hailing Jin and Amy deHart, University of California, Berkeley) Gene-for-gene resistance has been found to protect plants against different types of pathogens including bacteria, fungi, nematodes, and viruses. In the past few years, many R genes have been cloned from different plant species, which confer resistance to many types of pathogen. The dominant N gene from tobacco, cloned by transposon tagging, confers resistance to tobacco mosaic virus (TMV) in both tobacco and tomato.

Identification of signaling components in N-mediated TMV resistance

(Miki Yamamoto, UC Berkeley) The aim is to identify candidate resistance signaling genes, identify TMV defense signaling pathways in Solanaceae, and elucidate the role of son1 in R-gene mediated resistance and basal defense. Microarray analyses of tobacco mosaic virus (TMV)-challenged tomato were initiated to compare global gene expression patterns of wild-type (N) TMV-resistant, wild-type (n) TMV-susceptible, and enhanced susceptibility mutant, son1.

Virus induced gene silencing (VIGS) of the RB pathogen R gene for P. infestans resistance in S. bulbocastanum

(Hailing Jin, University of California, Berkeley) The focus of current efforts is on developing an efficient silencing system in tuber-generated potato in order to study the function of candidate genes responsible for certain disease resistance and its signaling pathways. S. bulbocastanum PT29, a wild diploid potato species, is highly resistant to all known races of P. infestans.

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