Salt stress induces the formation of a novel type of ‘pressure wood’ in two Populus species

Abstract

Summary• Salinity causes osmotic stress and limits biomass production of plants. The goal of this study was to investigate mechanisms underlying hydraulic adaptation to salinity.• Anatomical, ecophysiological and transcriptional responses to salinity were investigated in the xylem of a salt-sensitive (Populus · canescens) and a salt-tolerant species (Populus euphratica).• Moderate salt stress, which suppressed but did not abolish photosynthesis and radial growth in P. · canescens, resulted in hydraulic adaptation by increased vessel frequencies and decreased vessel lumina. Transcript abundances of a suite of genes (FLA, COB-like, BAM, XET, etc.) previously shown to be activated during tension wood formation, were collectively suppressed in developing xylem, whereas those for stress and defense-related genes increased. A subset of cell wall-related genes was also suppressed in salt-exposed P. euphratica, although this species largely excluded sodium and showed no anatomical alterations. Salt exposure influenced cell wall composition involving increases in the lignin : carbohydrate ratio in both species.• In conclusion, hydraulic stress adaptation involves cell wall modifications reciprocal to tension wood formation that result in the formation of a novel type of reaction wood in upright stems named 'pressure wood'. Our data suggest that transcriptional co-regulation of a core set of genes determines reaction wood composition.

Genomic insights into salt adaptation in a desert poplar

“…2b). HKT1 transporters have a key role in limiting Na þ transport from roots to shoots in Arabidopsis 19 , and may account for the lower rate of ion uptake and transport recorded in P. euphratica 9,20,21 . The gene family encoding P-type H þ -ATPases also had more copies in the P. euphratica genome than in the P. trichocarpa genome (Fig.…”

“…Populus euphratica is an excellent candidate for the analysis of salt tolerance 22 , as it displays apoplastic sodium accumulation and develops leaf succulence after prolonged salt exposure 8 . Consequently, in the last decade it has become a model for elucidating both physiological and molecular mechanisms of salt tolerance in tree species [5][6][7][8][9][10][11] . Using a newly developed fosmid-pooling strategy 14 , we sequenced and assembled the complex genome of P. euphratica with high heterozygosity and compared it with the closely related salt-sensitive model plant, P. trichocarpa.…”

“…Populus euphratica Oliv., which is native to desert regions ranging from western China to North Africa, is characterized by extraordinary adaptation to salt stress [5][6][7][8] . Notably, at high salinity it maintains higher growth and photosynthetic rates than other poplar species 9,10 and can survive concentrations of NaCl in nutrient solution up to 450 mM 11 .…”

The effects of putrescine are partly overlapping with osmotic stress processes in wheat

“…Pathogenesis-related protein 4 and pectinesterase inhibitor 12 have also been induced after PEG-induced osmotic stress, the latter one is an antifungal protein and may be involved in basal disease resistance, as well as in drought and oxidative stress tolerance in plants [34]. The induction of aluminium-induced protein with YGL and LRDR motifs, which also responded to salt stress in Populus genotypes, and has a role in xylem developing and it is involved in cell wall metabolism [35] was also found in wheat plants treated with PEG.…”

A Transcriptomic Network Underlies Microstructural and Physiological Responses to Cadmium in Populus × canescens

“…To obtain up-to-date annotations of differentially expressed genes, we performed several BLAST searches as described by Janz et al (2012). Briefly, the Affymetrix GeneChip poplar genome array target sequences were used to blast (BLASTn) against the Phytozome Populus trichocarpa version 2.2 transcript database.…”