Inhibition of the Plastidic ATP/ADP Transporter Protein Primes Potato Tubers for Augmented Elicitation of Defense Responses and Enhances Their Resistance against Erwinia carotovora

Abstract

Tubers of transgenic potato (Solanum tuberosum) plants with decreased activity of the plastidic ATP/ADP transporter AATP1 display reduced levels of starch, modified tuber morphology, and altered concentrations of primary metabolites. Here, we demonstrate that the spontaneous production of hydrogen peroxide, the endogenous content of salicylic acid, and the levels of mRNAs of various defense-related genes are similar in tuber discs of wild-type and AATP1(St) antisense plants. However, upon challenging the tissue with fungal elicitors or culture supernatants of the soft rot-causing pathogen Erwinia carotovora subsp. atroseptica, the AATP1(St) antisense tubers exhibit highly potentiated activation of defense responses when compared with wild-type tissue. The augmented defense responses comprise enhanced accumulation of transcripts of five defenserelated genes (␤-1,3-GLUCANASE B2 and A1, CHITINASE B3 and A2, and Phe AMMONIA-LYASE) and enhanced elicitation (up to 21-fold) of the early hydrogen peroxide burst. The potentiated activation of cellular defense responses in AATP1(St) antisense tubers is not accompanied by a precedent increase in endogenous salicylic acid levels, but is associated with a strongly enhanced resistance of the tissue to E. carotovora. From these results, we conclude that inhibition of primary metabolic reactions induces a primed state that sensitizes the potato tubers for improved elicitation of various cellular defense responses, which likely contribute to enhanced E. carotovora resistance.

Molecular characterization of two genes encoding plastidic ATP/ADP transport proteins in cassava

“…Antisense suppression of StAATP1 in potato has been demonstrated to result in not only decreased starch content in tubers, but also altered tuber morphology and the occurrence of adventitious budding (Tjaden et al 1998a). Antisense plants also exhibit enhanced resistance to Alternaria solani and Erwinia carotovora in tubers, while their leaves have increased resistance to Phytophthora infestans (Linke et al 2002;Conrath et al 2003). The basis for this improved pathogenic resistance remains unclear, but may be related to an increased capacity to release H 2 O 2 (Conrath et al 2003), a known trigger of plant defense genes (Orozco-Cárdenas et al 2001).…”

Jasmonoyl-l-Isoleucine Coordinates Metabolic Networks Required for Anthesis and Floral Attractant Emission in Wild Tobacco (Nicotiana attenuata)

“…MYB305 has been shown to regulate floral phenylpropanoid production, nectar secretion, and the accumulation of proteins such as NEC1 or Na-SWEET9, which together with its Arabidopsis homolog At-SWEET9 has recently been demonstrated to function as a sucrose efflux transporter essential for nectar secretion (Lin et al, 2014). The strongly reduced MYB305 transcript levels in nectary tissues of ir-aoc (Figure 6) increased after COR application, and this treatment also partly restored the nectar secretion in ir-aoc flowers ( Figure 6B).…”

“…Total RNA was extracted as described by Linke et al (2002). RNA extracts were treated with DNase using the DNA-free kit from Applied Biosystems/ Ambion.…”

Priming: Getting Ready for Battle

“…The spontaneous production of hydrogen peroxide, the endogenous content of SA, and the levels of transcripts of various defenserelated genes are similar in tuber disks of wild-type and StAATP1 antisense potato plants (Linke et al 2002). However, upon challenging the tissue with various fungal elicitors or culture supernatants of the bacterial pathogen Erwinia carotovora subsp.…”

“…This augmented defense included enhanced expression of defense-related genes and augmented incidence of early bursts of reactive oxygen species (ROS) (Linke et al 2002). The potentiated activation of cellular defense responses in StAATP1 plants was not preceded by an increase in endogenous SA levels but, nevertheless, coincided with a strongly enhanced resistance against E. carotovora (Linke et al 2002) and Alternaria solani (Conrath et al 2003) in the tubers or against Phytophthora infestans in the leaves (Conrath et al 2003). Thus, inhibition of steps in primary metabolism can lead to the induction of a primed state that sensitizes the tissue for improved elicitation of various cellular defense responses.…”