Wood Formation under Severe Drought Invokes Adjustment of the Hormonal and Transcriptional Landscape in Poplar

Abstract

Drought is a severe environmental stress that exerts negative effects on plant growth. In trees, drought leads to reduced secondary growth and altered wood anatomy. The mechanisms underlying wood stress adaptation are not well understood. Here, we investigated the physiological, anatomical, hormonal, and transcriptional responses of poplar to strong drought. Drought-stressed xylem was characterized by higher vessel frequencies, smaller vessel lumina, and thicker secondary fiber cell walls. These changes were accompanied by strong increases in abscisic acid (ABA) and antagonistic changes in salicylic acid in wood. Transcriptional evidence supported ABA biosynthesis and signaling in wood. Since ABA signaling activates the fiber-thickening factor NST1, we expected upregulation of the secondary cell wall (SCW) cascade under stress. By contrast, transcription factors and biosynthesis genes for SCW formation were down-regulated, whereas a small set of cellulose synthase-like genes and a huge array of genes involved in cell wall modification were up-regulated in drought-stressed wood. Therefore, we suggest that ABA signaling monitors normal SCW biosynthesis and that drought causes a switch from normal to “stress wood” formation recruiting a dedicated set of genes for cell wall biosynthesis and remodeling. This proposition implies that drought-induced changes in cell wall properties underlie regulatory mechanisms distinct from those of normal wood.

Chemical Composition and Related Properties of Lime (Tilia cordata Mill.) Bark and Wood as Affected by Tree Growth Conditions

“…Further, the more pronounced degree of differences in the chemical composition of bark than wood suggests that the bark is more sensitive to the environment than the wood. More specifically, changes in the contents of the cellulose, lignin and substances soluble in EtOH of bark of trees growing under three environmental stresses revealed that trees adopt certain physiological mechanisms to cope with the abiotic stresses [ 41 , 42 , 43 ].…”

Multi‐omics analysis of xylem sap uncovers dynamic modulation of poplar defenses by ammonium and nitrate

“…Xylem sap of high ammonium-fed poplars contained the highest PIP and NHP levels, whereas NHP was not significantly affected by low and medium nitrate supply, and was not detected under high nitrate supply (Figure 3d,e). ABA, which is important to coordinate the plant's stature and acclimation to drought (Fujita et al, 2005;Yu et al, 2019;Yu et al, 2021), was unaffected by differences in N supply in poplar xylem sap (Figure 3f). S3.…”

Salinity induces discontinuous protoxylem via aDELLA‐dependent mechanism promoting salt tolerance in Arabidopsis seedlings

“…1a). The diameter and shape of the SCWs are thought to influence hydraulic conductance, and the xylem shape correlates with drought resistance in many different species (Arend & Fromm, 2007; Awad et al ., 2010; Tang et al ., 2018; Yu et al ., 2021). Recently, we and others showed that xylem formation is plastic and responds to water availability.…”