Comparative transcriptome analysis of two citrus germplasms with contrasting susceptibility to Phytophthora nicotianae provides new insights into tolerance mechanisms

Abstract

Host perception of Phytophthora nicotianae switching to necrotrophy is fundamental for disease tolerance of citrus. It involves an HR-like response, strengthening of the cell wall structure and hormonal signaling. Stem rot caused by P. nicotianae is a worldwide disease of several important crops, including citrus. Given the growing awareness of chemical fungicides drawbacks, genetic improvement of citrus rootstocks remains the best alternative. However, the molecular basis underlying the successful response of resistant and/or tolerant genotypes remains poorly understood. Therefore, we performed a transcriptomic analysis to examine the differential defense response to P. nicotianae of two germplasms-tolerant sour orange (SO, Citrus aurantium) and susceptible Madam Vinous (MV, C. sinensis)-in both the biotrophic and necrotrophic phases of host-pathogen interaction. Our results revealed the necrotrophic phase as a decisive turning point, since it included stronger modulation of a number of genes implicated in pathogen perception, signal transduction, HR-like response, transcriptional reprogramming, hormone signaling, and cell wall modifications. In particular, the pathogen perception category reflected the ability of SO to perceive the pathogen even after its switch to necrotrophy, and thus to cope successfully with the infection, while MV failed. The concomitant changes in genes involved in the remaining functional categories seemed to prevent pathogen spread. This investigation provided further understanding of the successful defense mechanisms of C. aurantium against P. nicotianae, which might be exploited in post-genomic strategies to develop resistant Citrus genotypes.

Waterlogging Hardening Effect on Transplant Stress Tolerance in Pinus densiflora

“…In Populus tremula × Populus alba, there was a significant increase in phloem production in transgenic lines as LBD1-overexpressing, when auxin levels were lower in the tissues [91]. Furthermore, MYB TFs induce phenylpropanoid biosynthesis pathway genes, such as PAL, and activate the biosynthesis of lignin and cellulose in Arabidopsis and Populus [92][93][94][95]. Lignins are transported to the cell wall and plasma membrane only by ABCG29 in the ABC transporter [96].…”

The Transcriptome of Verticillium dahliae Responds Differentially Depending on the Disease Susceptibility Level of the Olive (Olea europaea L.) Cultivar

“…Indeed, an increasing body of knowledge is available on global genetic responses of host genotypes showing differential susceptibility to the attack of pathogens such as Phytophthora nicotianae in Citrus spp. [26], ‘ Candidatus Liberibacter asiaticus ’ in Citrus hystrix [27], Fusarium fujikuroi in rice [28], Xanthomonas perforans Race T3 in tomato [29], or Xylella fastidiosa in olive [30], just to name a few recent examples. For Verticillium spp., comparative transcriptomics have provided relevant information on the genetic basis underlying host tolerance/susceptibility in the pathosystems V. dahliae -olive [25] or V. nonalfalfae -hop ( Humulus lupulus L.) [31].…”