Moso bamboo (Phyllostachys edulis) is a well-known bamboo species of high economic value in the textile industry due to its rapid growth. Phytohormones, which are master regulators of growth and development, serve as important endogenous signals. However, the mechanisms through which phytohormones regulate growth in moso bamboo remain unknown to date. Here, we reported that exogenous gibberellins (GA) applications resulted in a significantly increased internode length and lignin condensation. Transcriptome sequencing revealed that photosynthesis-related genes were enriched in the GA-repressed gene class, which was consistent with the decrease in leaf chlorophyll concentrations and the lower rate of photosynthesis following GA treatment. Exogenous GA applications on seedlings are relatively easy to perform, thus we used 4-week-old whole seedlings of bamboo for GA- treatment followed by high throughput sequencing. In this study, we identified 932 cis-nature antisense transcripts (cis-NATs), and 22,196 alternative splicing (AS) events in total. Among them, 42 cis-nature antisense transcripts (cis-NATs) and 442 AS events were differentially expressed upon exposure to exogenous GA3, suggesting that post-transcriptional regulation might be also involved in the GA3 response. Targets of differential expression of cis-NATs included genes involved in hormone receptor, photosynthesis and cell wall biogenesis. For example, LAC4 and its corresponding cis-NATs were GA3-induced, and may be involved in the accumulation of lignin, thus affecting cell wall composition. This study provides novel insights illustrating how GA alters post-transcriptional regulation and will shed light on the underlying mechanism of growth modulated by GA in moso bamboo.

Genetic engineering technology has been successfully used in many plant species, but is limited in woody plants, especially in bamboos. Ma bamboo (Dendrocalamus latiflorus Munro) is one of the most important bamboo species in Asia, and its genetic improvement was largely restricted by the lack of an efficient regeneration and transformation method. Here we reported a plantlet regeneration and Agrobacterium-mediated transformation protocol by using Ma bamboo young shoots as explants. Under our optimized conditions, embryogenic calluses were successfully induced from the excised young shoots on callus induction medium (CIM) and rapidly grew on callus multiplication medium (CMM). Shoots and roots were regenerated on shoot induction medium (SIM) and root induction medium (RIM) respectively with high efficiency. An Agrobacterium-mediated genetic transformation protocol of Ma bamboo was established, verified by PCR and GUS staining. Furthermore, the maize Lc gene under the control of the ubiquitin promoter was successfully introduced into Ma bamboo genome and generated an anthocyanin over-accumulation phenotype. Our methods established here will facilitate the basic research as well as genetic breeding of this important bamboo species.

Bamboo covers over 30 million hectares of land across the world, and around 2.5 billion people are directly producing and consuming bamboo. However, probably it is the only major agronomic crop that is nearly impossible to make improvement by traditional breeding as the flowering time of most bamboos exceeds 70 years. Bamboo is the fastest growing plant on this planet, whearas, our knowledge on the underlying mechanisms is quite limited mainly due to the lack of efficient genetic manipulation tools. Therefore, the application of genetic engineering technology on bamboo is extremely important for its breeding and basic research. CRISPR (Clustered Regularly Interspaced Short Palindromic repeat)/Cas9 system provides straight forward ways for genome editing in many plants, but was never used in bamboo. In this study, we optimized the CRISPR/Cas9 elements in bamboo protoplast, and for the first time we established an efficient protocol for artificially producing the hexaploid bamboo mutant in its first generation by simultaneously targeting all homo‐alleles or specifically targeting one allele of a putative phytoene synthase gene through CRISPR/Cas9 technology. Furthermore, we produced a bamboo mutant with increased plant height by knocking out one Gibberelline‐responsive gene that we identified previously, which provides a good material for the future study on the molecular mechanism that controls the fast growth of bamboo.

Auxin is essential for plant growth and development. Although substantial progress has been made in understanding auxin pathways in model plants such as Arabidopsis and rice, little is known in moso bamboo which is famous for its fast growth resulting from the rapid cell elongation and division. Here we showed that exogenous auxin has strong effects on crown and primary roots. Genes involved in auxin action, including 13 YUCCA (YUC) genes involved in auxin synthesis, 14 PIN-FORMED/PIN-like (PIN/PILS) and 7 AUXIN1/LIKE-AUX1 (AUX1/LAX) members involved in auxin transport, 10 auxin receptors (AFB) involved in auxin perception, 43 auxin/indole-3-aceticacid (AUX/IAA) genes, and 41 auxin response factors (ARF) involved in auxin signaling were identified through genome-wide analysis. Phylogenetic analysis of these genes from Arabidopsis, Oryza sativa and bamboo revealed that auxin biosynthesis, transport, and signaling pathways are conserved in these species. A comprehensive study of auxin-responsive genes using RNA sequencing technology was performed, and the results also supported that moso bamboo shared a conserved regulatory mechanism for the expression of auxin pathway genes; meanwhile it harbors its own specific properties. In summary, we generated an overview of the auxin pathway in bamboo, which provides information for uncovering the precise roles of auxin pathway in this important species in the future.