Disease resistance gene transcription in transgenic potato is unaltered by temperature extremes and plant physiological age

Abstract

To date, several dozen plant disease resistance genes have been cloned from a variety of species. Despite successful efforts to isolate functional disease resistance genes and understand their roles in defence responses, surprisingly little is known about their transcriptional regulation. Global climate changes are expected to impact crop plant production, plant physiology and plant-microbe interactions. Understanding the impact of varying environmental and physiological factors on disease resistance gene transcript levels may be key to successful deployment. In this study we analyzed the expression patterns of the Phytophthora infestans resistance gene RB in transgenic potato plants across a broad range of temperatures and key physiological stages. Our results demonstrate that while temperature extremes have an obvious effect on plant morphology and development, RB is transcribed at all ages and temperatures in all genetic backgrounds. Quantitative analyses demonstrate that the RB transcript accumulates comparably throughout plant development, including at the tuber initiation stage. Implications for successful deployment of RB are discussed.

Influence of genetic background and plant age on expression of the potato late blight resistance gene Rpi‐phu1 during incompatible interactions with Phytophthora infestans

“…() demonstrated that although late blight resistance levels of plants with the RB gene in a compatible interaction differ depending on plant developmental stage (pre‐ and post‐flowering and senescence), RB transcript levels remain the same and cannot be responsible for this phenomenon. Another study tested flowering plants as well as 2‐ and 4‐week‐older ones and also detected no significant changes in RB transcript abundance (Iorizzo et al ., ). In both studies the R gene transcript levels were tested in uninoculated plants, while the present study also considered potential changes in Rpi‐phu1 transcription in the plant's response to the pathogen.…”

“…(), who applied avirulent P. infestans but only to transgenic plants. The present experiment on the influence of plant on Rpi‐phu1 expression differed from the previous ones, because, unlike other studies (Millett et al ., ; Iorizzo et al ., ), it was concerned not only with R gene transcript levels in uninoculated plants, but also with potential changes in Rpi‐phu1 transcription in the plant's response to the pathogen at different developmental stages.…”

“…Expression regulation studies have so far only been published for two R genes involved in interactions between potato and P. infestans, namely R3a and RB, and they have indicated rather diverse regulation patterns, even for the same R gene (Huang et al, 2005;Bradeen et al, 2009;Kramer et al, 2009;Millett et al, 2009;Iorizzo et al, 2011). While R3a transcription was investigated in transgenic plants inoculated with an incompatible P. infestans isolate (Huang et al, 2005), expression of RB has been measured in both transgenic and donor plants but using a compatible late blight isolate Kramer et al, 2009;Millett et al, 2009).…”

Solanum resistance genes against Phytophthora infestans and their corresponding avirulence genes

“…Comparatively few studies on SRpigs have addressed the expression of functional R genes. To fulfil a role as cellular sentinels, R proteins must be present in plant cells prior to attack, and therefore R genes are assumed to be constitutively expressed (Iorizzo et al ., ). The transcription of R3a (Huang et al ., ), RB (Song et al ., ) and Hero (Poch et al ., ) has indeed been observed in unchallenged leaves of S. tuberosum , S. bulbocastanum and S. lycopersicum , respectively.…”

“…Dark Red Norland, and therefore it is unlikely that the decrease in late blight resistance observed at increasing physiological age of potato plants is caused by changes in the expression of the RB transgene (Millett et al ., ). Similar transcript levels of RB within two RB transgenic potato lines at flowering, 2 weeks and 4 weeks after flowering, irrespective of the environmental temperature (10, 20 or 30 °C), further indicates little dependence of transcriptional activity on plant age and temperature (Iorizzo et al ., ). In RB ‐transformed potato cultivars, however, transgene copy number and transcript levels were positively correlated with late blight resistance (Bradeen et al ., ; Millett et al ., ), and RB transcript levels during the first 24 h post‐inoculation (hpi) were a major determinant of RB ‐mediated late blight resistance level (Kramer et al ., ).…”