Transcriptome responses of an ungrafted Phytophthora root rot tolerant avocado (Persea americana) rootstock to flooding and Phytophthora cinnamomi

Abstract

BackgroundAvocado (Persea americana Mill.) is a commercially important fruit crop worldwide. A major limitation to production is the oomycete Phytophthora cinnamomi, which causes root rot leading to branch-dieback and tree death. The decline of orchards infected with P. cinnamomi occurs much faster when exposed to flooding, even if flooding is only transient. Flooding is a multifactorial stress compromised of several individual stresses, making breeding and selection for tolerant varieties challenging. With more plantations occurring in marginal areas, with imperfect irrigation and drainage, understanding the response of avocado to these stresses will be important for the industry.ResultsMaintenance of energy production was found to be central in the response to flooding, as seen by up-regulation of transcripts related to glycolysis and induction of transcripts related to ethanolic fermentation. Energy-intensive processes were generally down-regulated, as evidenced by repression of transcripts related to processes such as secondary cell-wall biosynthesis as well as defence-related transcripts. Aquaporins were found to be down-regulated in avocado roots exposed to flooding, indicating reduced water-uptake under these conditions.ConclusionsThe transcriptomic response of avocado to flooding and P. cinnamomi was investigated utilizing microarray analysis. Differences in the transcriptome caused by the presence of the pathogen were minor compared to transcriptomic perturbations caused by flooding. The transcriptomic response of avocado to flooding reveals a response to flooding that is conserved in several species. This data could provide key information that could be used to improve selection of stress tolerant rootstocks in the avocado industry.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0893-2) contains supplementary material, which is available to authorized users.

Phytophthora cinnamomi

“…In addition to causing substantial economic losses in agriculture, forestry and horticulture, the inadvertent introduction of P. cinnamomi has had disastrous consequences for natural ecosystems and biodiversity. Prime examples include the impact of P. cinnamomi on chestnut and holm oak forests in Europe (Serrazina et al, 2015;Sghaier-Hammami et al, 2013), on avocado and macadamia worldwide (Akinsanmi et al, 2017;Reeksting et al, 2016) and on natural vegetation in south-east and south-west Australia (Cahill et al, 2008;Jung et al, 2013) (Fig. 1).…”

“…These unannotated data have been assembled into about 4000 contigs. At the time of writing, there were two published analyses of P. cinnamomi transcriptomes available (Meyer et al, 2016;Reitmann et al, 2016). The first reports data from Eucalyptus nitens, 5 days after inoculation with P. cinnamomi; the second reports data from a library of cysts and germinated cysts.…”

Time-resolved dual root-microbe transcriptomics reveals early induced Nicotiana benthamiana genes and conserved infection-promoting Phytophthora palmivora effectors

“…Phytophthora species [95,101] our data permitted the identification of early induced genes such as TIPTOP, a P. palmivora-responsive root tip promoter. An exciting future perspective is its exploitation for induced early resistance against Phytophthora root infections.…”

Genome-wide characterization deciphers distinct properties of major intrinsic proteins in six Phytophthora species

“…MIPs have a main role in water and solute transport and aid in homeostasis during plant stress responses (Afzal et al, 2016). Recently, transcriptome data provided important clues about the involvement of MIPs in host-pathogen interactions (Galindo-Gonzàlez and Deyholos, 2016; Reeksting et al, 2016; Guo et al, 2017). Although there has been no study on PMIPs, in the present study, we identified and characterized a total of 126 MIP homologues from the genomes of six Phytophthora species, which cause severe economic losses because of devastating effects on numerous agriculturally and ornamentally important plants (Tyler et al, 2006; Haas et al, 2009; Lamour et al, 2012; Thines, 2014; Fawke et al, 2015; Derevnina et al, 2016; Wang et al, 2016).…”