Moso bamboo is a bamboo plant resource with both efficient carbon sink and ecological and economic value. Bamboo shoots can achieve "explosive" growth in about 30 days. The nutrient supply mechanism behind it has long puzzled the academic community. Among them, how nitrogen, a key nutrient element, is dynamically allocated between mother bamboo and bamboo shoots and whip roots, and how its intrinsic gene expression is regulated, remains an unsolved mystery. Recently, the team of Professor Song Xinzhang of Zhejiang Agricultural and Forestry University and the team of Researcher Gao Zhimin of the International Center for Bamboo and Rattan used in situ isotope tracing and molecular biology combined analysis technology for the first time to reveal the spatiotemporal characteristics of nitrogen supply during the rapid growth period of Moso bamboo shoots, and elucidated the new molecular mechanism of transcription factor PeHDZ23987 regulating PeAAP29123 expression to mediate long-distance transport of amino acids, providing an important theoretical basis for precise fertilization of bamboo forests and helping to cultivate high-quality bamboo forests under the strategy of "replacing plastic with bamboo". The research results were published in Horticulture Research, an authoritative journal in the field of agricultural and forestry sciences, with the title "Stable isotope labelling and gene expression analysis reveal dynamic nitrogen-supply mechanisms for rapid growth of Moso bamboo".

The research team built a "one bamboo, one whip, one shoot" research system in the bamboo forest, and used 15N isotope tracing technology to accurately quantify the dynamic ratio of nitrogen supply from mother bamboo and whip roots to bamboo shoots during the rapid growth period of bamboo. The study found that in the early growth period of young shoots (7 days after the emergence of shoots), 72.5% of the nitrogen was transported unidirectionally by the mother bamboo through the bamboo whip; when entering the rapid growth period (21 days) and the branching period (34 days), the nitrogen contribution ratio of the mother bamboo and whip roots tended to be balanced (about 5:5); by the leaf expansion period (81 days), the whip root absorption contribution ratio jumped to 69.8%, forming a dynamic supply strategy of "mother bamboo-dominated-dual source balance-whip root-dominated" (Figure 1). The 15N reflux phenomenon (accounting for 30.4%) appeared in the leaves of the mother bamboo during the leaf expansion period, indicating that the direction of clonal integration changed with the development stage. This discovery provides a new perspective for the regulation of nutrient cycling in bamboo forests.

Figure 1 Dynamic synergistic distribution mechanism of nitrogen in mother bamboo, young shoots and bamboo rhizomes under different fertilization methods Transcriptome sequencing and gene co-expression network analysis revealed that the amino acid transporter encoded by PeAAP29123 is a key nitrogen transporter, and its expression level is significantly positively correlated with 15N content. Further studies found that the HD-ZIP family transcription factor PeHDZ23987 activates its expression by binding to specific elements of the PeAAP29123 promoter (Figure 2). Heterologous overexpression of PeAAP29123 and PeHDZ23987 in rice can significantly enhance the tolerance of transgenic rice to low nitrogen and improve nitrogen absorption efficiency.

Figure 2 PeHDZ23987 binds to the promoter element of PeAAP29123 and activates its expression. This study first constructed a "clonal division of labor-gene synergy" nutrient supply model and creatively proposed a balanced utilization strategy for the dynamic adjustment of nitrogen sources in time and space for bamboo, which not only ensures the rapid growth of young shoots but also avoids excessive consumption of mother bamboo. The research results fill the gap in the molecular mechanism of long-distance nitrogen transport in bamboo clonal plants and add a new dimension to the theory of plant nutritional ecology. Doctoral student Zhang Junbo, Associate Professor Shi Man, Postdoctoral Fellow Zhu Chenglei, and Young Teacher Yang Kebin of Qingdao Agricultural University are the co-first authors of the paper, and Professor Song Xinzhang is the corresponding author. Researcher Gao Zhimin of the International Center for Bamboo and Rattan, Professor Song Xiaoming of North China University of Technology, Associate Professor Li Quan, Associate Professor Cao Tingting, and Doctoral student Zhu Dezheng of Zhejiang A&F University also provided guidance and support for the study. The research was funded by the National Natural Science Foundation of China (31930075) and other projects.

Repost from Inbar: https://mp.weixin.qq.com/s/1CMimtDhJcKsG7I3gnyiBA