Morphological dissection and cellular and transcriptome characterizations of bamboo pith cavity formation reveal a pivotal role of genes related to programmed cell death

Abstract

Summary Pith cavity formation is critical for bamboo to overcome the bending force during its fast growth; however, the underlying molecular mechanisms remain largely unknown. Multiple approaches, including anatomical dissection, mathematical modelling and transcriptome profiling, were employed in this study to investigate the biology of pith cavity formation in bamboo Pseudosasa japonica . We found that the corruption of pith tissue occurred sequentially and asymmetrically from the top‐centre of the internode down to the bottom, which might be caused by the combined effects of asymmetrical radial and axial tensile forces during shoot‐wall cell elongation and spiral growth of bamboo internodes. Programmed cell death ( PCD ) in pitch manifested by TUNEL positive nuclei, DNA cleavage and degraded organelles, and potentially regulated by ethylene and calcium signalling pathway, ROS burst, cell wall modification, proteolysis and nutrient recycle genes, might be responsible for pith tissue corruption of Ps. japonica . Although similar physiological changes and transcriptome profiles were found in different bamboo species, different formation rates of pith cavity were observed, which might be caused by different pith cells across the internode that were negatively correlated with the culm diameter. These findings provided a systematical view on the formation of bamboo pith cavity and revealed that PCD plays an important role in the bamboo pith cavity formation.

Genome-wide identification, evolution and expression analysis of the aspartic protease gene family during rapid growth of moso bamboo (Phyllostachys edulis) shoots

“…Rapid growth of moso bamboo was observed shortly after the young shoots emerged from the ground [ 43 ]. GA is a critical phytohormone involved in rapid growth, and the spatial and temporal distribution of GA is strictly regulated [ 44 , 61 ]. The top portion of young bamboo shoots contain GA at a concentration higher than that in the basal portion [ 45 ].…”

“…Rapid growth of moso bamboo occurs after the young bamboo shoots are covered with a shell and emerge from the ground. PCD was revealed to occur in pith cavity formation during rapid bamboo growth [ 44 ]. During the bamboo rapid-growth stage, cell division gradually decreases, while cell elongation and secondary cell wall thickening also occur [ 45 , 46 ].…”

Gene Set Subtraction Reveals 633 Candidate Genes for Bamboo Culm Wall Thickening

“…It has been shown that the shoot apical meristem (SAM) plays an important role in the development of bamboo culm wall thickening. A larger SAM leads to elevated levels of hormones (e.g., cytokinin and growth hormone) and upregulation of hormone signaling and downstream functional genes (e.g., metabolism-related genes), ultimately leading to thickening of the bamboo culm wall [41]. The growth of SAM requires large amounts of energy and nutrients, which is consistent with the results of this study showing that many differential genes are enriched in the metabolic pathway of starch and sucrose and oxidative phosphorylation.…”

The Generalized Gielis Geometric Equation and Its Application

“…where n is a real number. This equation has been shown to be valid for describing the actual cross-sections of tree rings and bamboo shoots [2][3][4][5]. Equation (3) in polar coordinates can be rewritten as…”

“…where n 1 , n 2 and n 3 are constants (both ∈ R); positive integer m was introduced to make the curve generate arbitrary polygons (with m angles) consequently enhancing the flexibility of Lamé curves. We refer to Equation (5) as the original Gielis equation (OGE) in the following text for simplicity. OGE has been used to simulate many natural shapes, e.g., diatoms, eggs, cross sections of plants, snowflakes and starfish [1,2].…”