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During flooding in the Water Level Fluctuation Zone (WLFZ), nutrient levels of nitrogen (N) and phosphorus (P) in the overlying water fluctuate due to soil nutrient release, impacting the decomposition of plants like Cynodon dactylon. However, limited research on the effects of these nutrient changes on plant nutrient release and water dynamics complicates accurate assessments of water quality impacts. This study used 8 water samples with varying initial nutrient levels to simulate N and P changes induced by WLFZ soil nutrients and examined the decomposition and nutrient dynamics of Cynodon dactylon. Results showed that flooding significantly increased initial levels of N and P, especially as particulate nitrogen (PN) and particulate phosphorus (PP), affecting both plant decomposition and nutrient dynamics in the water. After 60 days, Cynodon dactylon lost 47.97%-56.01% dry matter, 43.58%-54.48% total nitrogen (TN), and 14.28%-20.50% total phosphorus (TP). Initial PN and total dissolved nitrogen (TDN) promoted dry matter loss, PN and PP promoted TP loss, while PN and TDN inhibited TN loss. By day 60, no positive correlation was found between plant-released N and P and TN or TP in the overlying water. However, initial PP and PN levels were negatively correlated with TN and TP, indicating an inhibitory effect. Further analysis indicates that PN and PP released from the soil supported the formation of microbial aggregates, enhancing denitrification and phosphorus removal and thus improving water purification over time. [ABSTRACT FROM AUTHOR]

Cellulose, which can be converted into numerous industrial products, has important impacts on the global economy. It has long been known that cellulose synthesis in plants is tightly regulated by various phytohormones. However, the underlying mechanism of cellulose synthesis regulation remains elusive. Here, we show that in rice (Oryza sativa), gibberellin (GA) signals promote cellulose synthesis by relieving the interaction between SLENDER RICE1 (SLR1), a DELLA repressor of GA signaling, and NACs, the top-layer transcription factors for secondary wall formation. Mutations in GA -related genes and physiological treatments altered the transcription of CELLULOSE SYNTHASE genes (CESA s) and the cellulose level. Multiple experiments demonstrated that transcription factors NAC29/31 and MYB61 are CESA regulators in rice; NAC29/31 directly regulates MYB61 , which in turn activates CESA expression. This hierarchical regulation pathway is blocked by SLR1-NAC29/31 interactions. Based on the results of anatomical analysis and GA content examination in developing rice internodes, this signaling cascade was found to be modulated by varied endogenous GA levels and to be required for internode development. Genetic and gene expression analyses were further performed in Arabidopsis thaliana   GA -related mutants. Altogether, our findings reveal a conserved mechanism by which GA regulates secondary wall cellulose synthesis in land plants and provide a strategy for manipulating cellulose production and plant growth. [ABSTRACT FROM AUTHOR]

Xylan, a pivotal polymer with diversified structures, is indispensable for cell wall integrity and contributes to plant growth and biomass recalcitrance. Xylan is synthesized by multienzyme complexes named xylan synthase complexes (XSCs). However, the biochemical mechanism of XSCs and the functions of core components within XSC remain unclear. Here, we report that rice (Oryza sativa) XYLAN O-ACETYLTRANSFERASE 6 (XOAT6) and the xylan synthase IRREGULAR XYLEM10 (IRX10) represent core components of the XSC, acting together to biosynthesize acetyl-xylans. Co-fractionation mass spectrometry and protein-protein interaction analyses revealed that IRX10 and XOAT6 physically interact within XSC, corroborated by similar xylan defects in xoat6 and irx10 mutants. Biochemical assays showed that XOAT6 is an O-acetyltransferase of the xylan backbone and facilitates chain polymerization catalyzed by IRX10. Fluorescence correlation spectroscopy further visualized the xylooligomer polymerization process at a single-molecule level. Solid-state NMR analysis, electron microscopy observations, and nanoindentation examinations identified the altered xylan conformation, disorganized cellulosic structure, and increased wall rigidity and cellulose accessibility in the mutants, leading to brittleness and improved saccharification efficiency. Our findings provide insights into the assembly of XSCs and xylan biosynthesis and offer a framework for tailoring xylans to improve crop traits and biomass., Competing Interests: Conflict of interest statement. The authors declare no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)