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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Agricultural Systems Laboratory » Research » Publications at this Location » Publication #326728
Title: Pathogenesis-related protein 1b1 (PR1b1) is a major tomato fruit protein responsive to chilling temperature and upregulated in high polyamine transgenic genotypes

Author
item GOYAL, RAVINDER - Lethbridge Research Center
item FATIMA, TAHIRA - Former ARS Employee
item TOPUZ, MUHAMET - Former ARS Employee
item BERNADEC, ANNE - Institut National De La Recherche Agronomique (INRA)
item Sicher Jr, Richard
item HANDA, AVTAR - Purdue University
item Mattoo, Autar

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2016
Publication Date: 6/22/2016
Citation: Goyal, R.K., Fatima, T., Topuz, M., Bernadec, A., Sicher Jr, R.C., Handa, A.K., Mattoo, A.K. 2016. Pathogenesis-related protein 1b1 (PR1b1) is a major tomato fruit protein responsive to chilling temperature and upregulated in high polyamine transgenic genotypes. Frontiers in Plant Science. 7:901.

Interpretive Summary: Plants are sessile and therefore have evolved mechanisms to respond to the vagaries of nature, including temperature extremes. At low temperatures, growth, quality and productivity of plants can be compromised. Tomato is a chilling sensitive plant and the fruits succumb to chilling injury when stored or held at temperatures below 15 C. This susceptibility limits their shelf life and causes substantial economic losses. Low temperature tolerance is a complex, quantitative trait with molecular mechanisms yet to be fully understood. Our laboratory has developed tomato lines that express important growth regulator and stress deflators called polyamines, particularly the higher polyamines spermidine and spermine. In order to define the mechanisms that polyamines use to protect plants against chilling sensitivity, we tested these transgenic lines to look for a marker protein. We demonstrated that these tomato lines when exposed to chilling temperatures and re-warmed thereafter accumulated a protein of ~ 14 kiloDaltons. Surprisingly, this protein was identified as the pathogenesis-related 1b1 (PR1b1) protein using proteomics, sequencing and immunological approaches. Longer half-life of polyamines in the two transgenic tomato fruit induced further stabilization and a longer half-life of the PR1b1 protein. Since cold initiates polyamine accumulation prior to re-warming, we speculate that polyamines prime the fruits to contain any possible pathogen infection via activation of the PR1b1 gene and accumulation of its protein product. Such a function for enhancement of polyamine levels together with stabilization of the PR1b1 protein is proposed as a pre-emptive plant defense mechanism involving Cold Stress-Induced Disease Resistance (SIDR). These novel findings are important for horticulturists, plant pathologists, molecular biologists and the fruit industry interested in developing cold resistant germplasm.

Technical Abstract: Plants execute an array of mechanisms in response to stress which include upregulation of defense-related proteins and changes in specific metabolites. A group of commonly found metabolites implicated in protection against stresses such as chilling stress constitute ubiquitous biogenic amines called polyamines – putrescine (Put), spermidine (Spd), spermine (Spm), thermo-Spm. Tomato is a cold sensitive plant; fruits of which undergo chilling injury at temperatures below 15 C. We utilized two transgenic tomato lines that express yeast S-adenosylmethionine decarboxylase and whose fruits accumulate Spd and Spm together with a control line (Mehta et al., 2002), to address chilling-injury signaling. Exposure to chilling temperature (2 C) led to a several-fold increase in the Put content in all the lines, and upon re-warming of the fruits at 20 C, the levels of Spd and Spm increased further in the fruit of the two transgenic lines, the higher levels remaining stable for 15 days after re-warming as compared to the fruit from the control line. Profiling their steady state proteins before and after re-warming highlighted a protein of ~ 14 kD. Using a proteomics approach, protein sequencing and immunoblotting, the ~ 14-kD protein was identified as the pathogenesis related protein 1b1 (PR1b1). The PR1b1 protein accumulated transiently in the control fruit but its level in the two Spd/Spm-accumulating fruit increased and remained stable till 15 days post warming. PR1b1 gene transcripts were found to accumulate transiently in all the lines but were several-fold higher in the transgenic lines than the control fruit. The chilling-induced increase in the PR1b1 protein seemed to be regulated post-transcriptionally and independent of the signaling via plant hormones ethylene and methyl jasmonate, but was possibly linked to salicylic acid. We propose that polyamine-mediated sustained accumulation of PR1b1 protein in chilled tomato fruit during re-warming could be a pre-emptive plant defense mechanism related to Cold Stress-Induced Disease Resistance (SIDR).