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Summary: Moso bamboo (Phyllostachys edulis) known as Mao Zhu (MZ) in Chinese exhibits various forms with distinct morphological characteristics. However, the evolutionary relationship among MZ forms and the mechanisms of culm shape variation are still lacking. Here, the main differences among MZ forms were identified as culm shape variation, which were confirmed by analysing MZ forms (799 bamboo culms) and MZ (458 bamboo culms) populations. To unravel the genetic basis underlying the morphological variations, 20 MZ forms were subjected to whole‐genome resequencing. Further analysis yielded 3 230 107 high‐quality SNPs and uncovered low genetic diversity and high genotype heterozygosity associated with MZ forms' formation. By integrating the SNP data of 427 MZ individuals representing 15 geographic regions, the origins of eight MZ forms were successfully traced using the phylogenetic tree and the identified common heterozygous loci. Meanwhile, transcriptomic analysis was performed using shoots from MZ and its two forms with culm shape variation. The results, combined with genomic analyses, demonstrated that hormone signalling related genes played crucial roles in culm variation. Co‐expression network analysis uncovered genes associated with multiple plant hormone signal transduction, especially auxin and cytokinin were involved in culm shape variation. Furthermore, the regulatory relationships of a specific transcription factor and their target genes associated with auxin and ethylene signalling were validated by yeast one‐hybrid, electrophoretic mobility shift assays, and dual‐luciferase reporter. Overall, this study provides important insights into the culm shape variation formation in bamboo, which facilitates to breed new varieties with novel culms. [ABSTRACT FROM AUTHOR]

ROOTHAIRLESS (RHL) is a typical type of basic helix‐loop‐helix (bHLH) transcription factor (TF), which has been reported to participate in various aspects of plant growth and in response to stress. However, the functions of RHL subfamily members in moso bamboo (Phyllostachys edulis) remain unknown. In this study, we identified 14 bHLH genes (PeRHL1–PeRHL14) in moso bamboo. Phylogenetic tree and conserved motif analyses showed that PeRHLs were clustered into three clades. The expression analysis suggested that PeRHL4 was co‐expressed with PeTIP1‐1 and PePHT1‐1 in moso bamboo. Moreover, these three genes were all up‐regulated in moso bamboo under drought stress and phosphate starvation. Y1H, DLR and EMSA assays demonstrated that PeRHL4 could activate the expression of PeTIP1‐1 and PePHT1‐1. Furthermore, overexpression of PeRHL4 could increase both drought and phosphate starvation tolerance in transgenic rice, in which the expression of OsTIPs and OsPHT1s was significantly improved, respectively. Overall, our results indicated that drought stress and phosphate starvation could induce the expression of PeRHL4, which in turn activated downstream genes involved in water and phosphate transport. Collectively, our findings reveal that PeRHL4 acting as a positive regulator contributes to enhancing the tolerance of moso bamboo under drought stress and phosphate starvation. Summary statement: Drought stress and phosphate starvation trigger intricate signalling networks that impact plant growth. This study presents PeRHL4 as a regulatory factor to activate downstream genes for water and phosphate transport, potentially bolstering the tolerance of moso bamboo under stresses. [ABSTRACT FROM AUTHOR]

Summary: Water plays crucial roles in expeditious growth and osmotic stress of bamboo. Nevertheless, the molecular mechanism of water transport remains unclear.In this study, an aquaporin gene, PeTIP4‐3, was identified through a joint analysis of root pressure and transcriptomic data in moso bamboo (Phyllostachys edulis). PeTIP4‐3 was highly expressed in shoots, especially in the vascular bundle sheath cells. Overexpression of PeTIP4‐3 could increase drought and salt tolerance in transgenic yeast and rice.A co‐expression pattern of PeSAPK4, PeMYB99 and PeTIP4‐3 was revealed by WGCNA. PeMYB99 exhibited an ability to independently bind to and activate PeTIP4‐3, which augmented tolerance to drought and salt stress. PeSAPK4 could interact with and phosphorylate PeMYB99 in vivo and in vitro, wherein they synergistically accelerated PeTIP4‐3 transcription. Overexpression of PeMYB99 and PeSAPK4 also conferred drought and salt tolerance in transgenic rice.Further ABA treatment analysis indicated that PeSAPK4 enhanced water transport in response to stress via ABA signaling. Collectively, an ABA‐mediated cascade of PeSAPK4‐PeMYB99‐PeTIP4‐3 is proposed, which governs water transport in moso bamboo. [ABSTRACT FROM AUTHOR]

ABSTRACT Drought drastically affects plant growth, development and productivity. Plants respond to drought stress by enhancing sugar accumulation and water transport. Homeodomain‐leucine zipper (HD‐Zip) transcription factors (TFs) participate in various aspects of plant growth and stress response. However, the internal regulatory mechanism of HD‐Zips in moso bamboo (Phyllostachys edulis) remains largely unknown. In this study, we identified an HD‐Zip member, PeHDZ72, which was highly expressed in bamboo shoots and roots and was induced by drought. Furthermore, PeSTP_46019, PeSWEET_23178 and PeTIP4‐3 were identified as downstream genes of PeHDZ72 in moso bamboo by DAP‐seq. The expressions of these three genes were all induced by drought stress. Y1H, DLR and GUS activity assays demonstrated that PeHDZ72 could bind to three types of HD‐motifs in the promoters of these three genes. Overexpression of PeHDZ72 led to a remarkable enhancement in drought tolerance in transgenic rice, with significantly improved soluble sugar and sucrose contents. Meanwhile, the expressions of OsSTPs, OsSWEETs and OsTIP were all upregulated in transgenic rice under drought stress. Overall, our results indicate that drought stress might induce the expression of PeHDZ72, which in turn activated downstream genes PeSTP_46019, PeSWEET_23178 and PeTIP4‐3, contributing to the improvement of cellular osmotic potential in moso bamboo in response to drought stress. [ABSTRACT FROM AUTHOR]

The lignocellulosic feedstock of woody bamboo shows promising potential as an alternative to conventional wood, attributed to its excellent properties. The content and distribution of lignin serve as the foundation of these properties. While the regulation of lignin biosynthesis in bamboo has been extensively studied at the transcriptional level, its posttranslational control has remained poorly understood. This study provides a ubiquitinome dataset for moso bamboo (Phyllostachys edulis), identifying 13015 ubiquitinated sites in 4849 unique proteins. We further identified Kelch repeat F-boxprotein 9 (PeKFB9) that plays a negative role in lignin biosynthesis. Heterologous expression of PeKFB9 resulted in reduced accumulation of lignin and decreased phenylalanine ammonia-lyase (PAL) activities. Both in vitro and in vivo assays identified interaction between PeKFB9 and PePAL10. Further examination revealed that SCFPeKFB9 mediated the ubiquitination and degradation of PePAL10 via the 26S proteasome pathway. Moreover, PebZIP28667 could bind to the PePAL10 promoter to significantly inhibit its transcription, and ubiquitination of PebZIP28667 weakened this inhibition. Collectively, our findings reveal a PeKFB9-PePAL10/PebZIP28667-PePAL10 module that acts as a negative regulator of lignin biosynthesis. This study advances our understanding of posttranslational regulation in plant lignification, which will facilitate the improvement of the properties of bamboo wood and the breeding of varieties., (© 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.)