In addition to post-transcriptional regulation by alternative splicing (AS), natural antisense transcripts (NATs) also play important roles. Although endogenous hormone studies have been conducted in the shoots of moso bamboo, the direct link between hormone activity and post-transcriptional regulation remains unknown. Proteins involved in cell wall biosynthesis are reported to be related to rapidly elongating bamboo culms. Cellulose fibrils maximize longitudinal elasticity while lignification primarily increases the transversal rigidity of the fibrils, which overall provides structural support.
Lignin, a main resource for biofuels, functions as a transport vessel to maintain the structural and mechanical integrity of the entire plant. The extensibility of moso bamboo cell walls is a key factor in moso bamboo’s growth, as they allow grow to great heights due to the two primary components of bamboo walls, cellulose and lignin. The concentration of endogenous GA 3, one of most common bioactive forms of gibberellic acid, displays bimodal variation when the above-ground heights grow from 0.05 m to 12 m in moso bamboo. A later proteomics study showed seven protein spots involved in hormone biosynthesis during shoot development. Transcriptome analysis in the shoots of moso bamboo revealed hormone-related genes are involved in both growth directions, that is in height and in thickness. Moso bamboo, native to China and Taiwan, is now grown worldwide for commercial purposes thanks to its very fast growth. GA regulate growth by suppressing a group of DELLA nuclear repressor proteins, and display extensive cross-talk with other hormone signaling pathways, including auxin and brassinosteroids (BR). Gibberellins (GA), are one of the most important class of growth-promoting phytohormones, play crucial roles in many aspects of plant growth and development, especially in growth promotion and flower induction. For example, LAC4 and its corresponding cis-NATs were GA 3-induced, and may be involved in the accumulation of lignin, thus affecting cell wall composition. Targets of differential expression of cis-NATs included genes involved in hormone receptor, photosynthesis and cell wall biogenesis. Among them, 42 cis-nature antisense transcripts ( cis-NATs) and 442 AS events were differentially expressed upon exposure to exogenous GA 3, suggesting that post-transcriptional regulation might be also involved in the GA 3 response. In this study, we identified 932 cis-nature antisense transcripts ( cis-NATs), and 22,196 alternative splicing (AS) events in total. 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. 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. Here, we reported that exogenous gibberellins (GA) applications resulted in a significantly increased internode length and lignin condensation.
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