Pathogenesis-Related Protein 1b1 (PR1b1) Is a Major Tomato Fruit Protein Responsive to Chilling Temperature and Upregulated in High Polyamine Transgenic Genotypes

Abstract

Plants execute an array of mechanisms in response to stress which include upregulation of defense-related proteins and changes in specific metabolites. Polyamines – putrescine (Put), spermidine (Spd), and spermine (Spm) – are metabolites commonly found associated with abiotic stresses such as chilling stress. We have generated two transgenic tomato lines (556HO and 579HO) that express yeast S-adenosylmethionine decarboxylase and specifically accumulate Spd and Spm in fruits in comparison to fruits from control (556AZ) plants (Mehta et al., 2002). Tomato fruits undergo chilling injury at temperatures below 13°C. The high Spd and Spm tomato together with the control azygous line were utilized to address role(s) of polyamines in chilling-injury signaling. Exposure to chilling temperature (2°C) led to several-fold increase in the Put content in all the lines. 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 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 whose level was barely detectable at d 15 post-warming while in the fruit from both the 556HO and 579HO transgenic lines PR1b1 abundance increased and remained stable till d 15 post warming. PR1b1 gene transcripts were found low in the control fruit with a visible accumulation only on d 15 post warming; however, in both the transgenic lines it accumulated and increased soon after rewarming being several-fold higher on day 2 while in 556HO line this increase continued until d 6 than the control fruit. The chilling-induced increase in PR1b1 protein seems independent of ethylene and methyl jasmonate signaling but may be linked to salicylic acid. We propose that polyamine-mediated sustained accumulation of PR1b1 protein in post-warmed chilled tomato fruit is a pre-emptive cold stress response and possibly a defense response mechanism related to Cold Stress-Induced Disease Resistance (SIDR) phenomenon.

Heat Shock-Induced Resistance Against Pseudomonas syringae pv. tomato (Okabe) Young et al. via Heat Shock Transcription Factors in Tomato

“…In tomato, PR1b1 with distinct HSE structure has been extensively studied as a major protein responsive to chilling temperature. Exposure of tomato fruits to chilling temperature (2 • C) followed by re-warming of the fruits at 20 • C led to a several-fold increase in PR1b1 content [37]. This result confirmed that PR1b1 was responsive to changes in temperature.…”

Polyamines: Bio-Molecules with Diverse Functions in Plant and Human Health and Disease

“…Our current understanding of the roles PAs play was intensified and emerged through genetic evidence obtained through the characterization of mutations in the PA biosynthetic pathway and analyzing molecular, biochemical and physiological changes in specific transgenic organisms altered in the levels of a particular PA or PAs (Mehta et al, 2002 ; Mattoo et al, 2006 , 2010 ; Sriva et al, 2007 ; Sobolev et al, 2014 ; Kusano and Suzuki, 2015 ; Fatima et al, 2016 ; Goyal et al, 2016 ; Pegg, 2016 ). It has become apparent that PA function is dependent upon the cellular level of each PA, likely differentiable and specific to each diamine, triamine and tetramine (Put, Spd, and Spm, respectively) (Handa and Mattoo, 2010 ; Mattoo et al, 2010 ), and in many instances being temperature-dependent (Mattoo, 2014 ; Liu et al, 2015 ; Goyal et al, 2016 ). Further understanding of how living cells achieve PA homeostasis and which master regulators regulate their biosynthesis, interconversion, catabolism and conjugation to bring about desirable biologically active cellular concentrations to impact specific biological processes in normal and stressful environment(s) is necessary to fully appreciate their functions in different biological systems.…”

Proteomic Analysis of Differentially Accumulated Proteins in Cucumber (Cucumis sativus) Fruit Peel in Response to Pre-storage Cold Acclimation

“…Pathogenesis- related (PR) proteins are expressed in plants in response to biotic and abiotic stresses (Renaut et al, 2006 ) and several groups of PR proteins are responsive to low temperature. The PR protein 1b1 is a major protein responsive to chilling temperature in tomato fruit and is up-regulated in high polyamine transgenic genotypes (Goyal et al, 2016 ). Thaumatin-like proteins might play important roles against chilling stress in peach fruit (Dagar et al, 2010 ).…”