ArabidopsisXTH4andXTH9contribute to wood cell expansion and secondary wall formation

Abstract

31 Tel: 46 (0)90 786 8367 32 Fax: 46 (0)90-786 8165 33 34 Short Title: XTH4 and XTH9 affect secondary xylem differentiation 35 36 One sentence summary: XTH4 and XTH9 positively regulate xylem cell expansion and fiber 37 intrusive tip growth, and their deficiency alters secondary wall formation via cell wall 38 integrity sensing mechanisms. 39 40 AUTHOR CONTRIBUTION 41 SK analyzed cell wall composition, mutant growth, and gene expression, and wrote the 42 manuscript; AB analyzed hypocotyl phenotypes and xylem cell morphology in mutants, 43 discovered secondary wall phenotypes, and carried immunolocalization, NN isolated and 44 purified mutants and created OE plants, MDM and MM analyzed cell walls by in situ Raman 45 and in situ FTIR, SE created GUS reporter lines, VK analyzed Populus XTH genes and their 46 expression in AspWood, LG and SMM carried out saccharification analyses, AG interpreted 47 53 Chemistry of Umeå University for the Vibrational Spectroscopy Core Facility, Bio4Energy 54 and TC4F support for Plant Analytical Biopolymer platform, and Vinnova (the Swedish 55 Governmental Agency for Innovation Systems) and KAW (The Knut and Alice Wallenberg 56 Foundation) support for plant growth facility are acknowledged. The research projects were 57 funded by SSF (ValueTree project RBP14-0011), Formas and VR grants to EJM. 58 3 59 60 KEYWORDS 61 Xyloglucan, XET, secondary wall, lignin, secondary xylem, wood development, xylogenesis, 62 microspectroscopy, Raman spectroscopy, FTIR spectroscopy, cell wall integrity sensing 63 64 SIGNIFICANCE STATEMENT 65 Xyloglucan is a ubiquitous component of primary cell walls in all land plants but has not 66 been so far reported in secondary walls. It is metabolized in muro by cell wall-residing 67 enzymes -xyloglucan endotransglycosylases/hydrolases (XTHs), which are reportedly 68 abundant in vascular tissues, but their role in these tissues is unclear. Here we report that two 69 vascular expressed enzymes in Arabidopsis, XTH4 and XTH9 contribute to the secondary 70 xylem cell radial expansion and intrusive elongation in secondary vascular tissues. 71 Unexpectedly, deficiency in their activities highly affect chemistry and ultrastructure of 72 secondary cell walls by non-cell autonomous mechanisms, including transcriptional induction 73 of secondary wall-related biosynthetic genes and cell wall integrity sensors. These results link 74 xyloglucan metabolism with cell wall integrity pathways, shedding new light on previous 75 reports about prominent effects of xyloglucan metabolism on secondary walls. 76 77 ABSTRACT 78In dicotyledons, xyloglucan is the major hemicellulose of primary walls affecting the load-79 bearing framework with participation of XTH enzymes. We used loss-and gain-of function 80 approaches to study functions of abundant cambial region expressed XTH4 and XTH9 in 81 secondary growth. In secondarily thickened hypocotyls, these enzymes had positive effects 82 on vessel element expansion and fiber intrusive growth. In addition, they stimulated 83 secondary wall thic...

Meta-Analysis of Public RNA Sequencing Data of Abscisic Acid-Related Abiotic Stresses inArabidopsis thaliana

“…AtXTH4 and AtXTH9 contribute to the regulation of xylem cell expansion and secondary growth, including the production of secondary xylem and the accumulation of secondary walls. However, the function of stress conditions has not yet been clarified (Kushwah et al, 2020). These studies suggested that XTH plays an important role in various stress responses.…”

High-order mutants reveal an essential requirement for peroxidases but not laccases in Casparian strip lignification

“…Indeed, endodermal lignification occurs in the cell walls between two endodermal cells that amount to a total thickness of barely 200 nm (3,31), very different in dimension from lignified secondary walls, which in the case of interfascicular fibers can be tenfold thicker (ca. 2 µm) (50,51). Beyond this, primary and secondary walls also differ in composition and abundance of their cellulose, hemi-cellulose and pectin components (52,53).…”

Transcriptional signatures associated with waterlogging stress responses and aerenchyma formation in barley root tissue

“…The copyright holder for this preprint this version posted October 10, 2023. ; https://doi.org/10.1101/2023.10.06.561260 doi: bioRxiv preprint and was identified as hypoxia responsive in Prunus rootstock microarray analysis (Rubio-Cabetas et al, 2018). Likewise, XTH16 was upregulated by hypoxia in tomato root tissue (Safavi-Rizi et al, 2020); while XTH4 is associated with cell wall structure modulation in Arabidopsis (Kushwah et al, 2020) and fluctuates in expression depending on the root location sampled in aerenchyma forming sugarcane roots, with root segments with largest proportion of aerenchyma tissue having highest expression levels of XTH4 (Grandis et al, 2019). Finally, AT3G08030 is implicated in remodelling of the cell wall and response to a number of stresses in Arabidopsis (Cruz-Valderrama et al, 2019) and has been classified as a molecular marker of seed aging (Garza-Caligaris et al, 2012) but was not previously been connected with waterlogging stress or aerenchyma formation.…”