2026-07-08 マサチューセッツ大学アマースト校
＜関連情報＞
- https://www.umass.edu/news/article/grasses-provide-most-worlds-calories-were-only-now-starting-learn-how-they-grow
- https://www.cell.com/current-biology/abstract/S0960-9822(26)00745-1
- https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0100072
温度信号が草の二次細胞壁の肥厚を促進する Temperature signals drive grass secondary cell wall thickening
Greg A. Gregory ∙ Bahman Khahani ∙ Joshua H. Coomey ∙ … ∙ Kira A. Gardner ∙ David Follette ∙ Samuel P. Hazen
Current Biology Published:July 6, 2026
DOI:https://doi.org/10.1016/j.cub.2026.06.034
Highlights
- Thermocycles, not light or the circadian clock, drive CESA8 rhythms
- CESA8 expression increases during cool nights and declines during warm days
- Secondary-wall gene expression is coordinated with stem elongation
- Warm and cold pulses trigger opposing responses, explained by an incoherent feedforward loop model
Summary
Secondary cell wall thickening is essential for plant structural development, providing the mechanical strength and rigidity required for upright growth. However, direct observation of this process in its endogenous developmental context within living plants has remained limited. Cellulose, the predominant component of secondary walls and the most abundant biopolymer on Earth, is synthesized at the plasma membrane by complexes containing CELLULOSE SYNTHASE A (CESA) proteins. Despite its central role, the precise timing and regulation of cellulose deposition during plant development remain unclear. To address this gap, we developed a real-time bioluminescence imaging system in the model grass Brachypodium distachyon using a luciferase transcriptional reporter driven by the CESA8 cis-regulatory region. Bioluminescence imaging revealed a consistent spatial pattern of CESA8 expression within elongating internodes, coinciding with regions undergoing secondary wall deposition and progressive increases in cellulose crystallinity. Time-lapse imaging showed that expression follows a robust daily rhythm driven by temperature cycles, independent of light or endogenous circadian signals. Temperature-pulse experiments uncovered rapid, transient inverse responses that were accurately predicted by a mathematical model based on an incoherent feedforward loop. CESA8 expression correlated strongly with stem elongation, linking structural reinforcement with temperature-driven shoot growth in grasses.
ブラキポディウム・ディスタキオンの成長速度は、概日時計ではなく、日々の温度変化によって調節される Daily Changes in Temperature, Not the Circadian Clock, Regulate Growth Rate in Brachypodium distachyon
Dominick A. Matos,Benjamin J. Cole,Ian P. Whitney,Kirk J.-M. MacKinnon,Steve A. Kay,Samuel P. Hazen
PLOS One Published: June 13, 2014
DOI:https://doi.org/10.1371/journal.pone.0100072
Abstract
Plant growth is commonly regulated by external cues such as light, temperature, water availability, and internal cues generated by the circadian clock. Changes in the rate of growth within the course of a day have been observed in the leaves, stems, and roots of numerous species. However, the relative impact of the circadian clock on the growth of grasses has not been thoroughly characterized. We examined the influence of diurnal temperature and light changes, and that of the circadian clock on leaf length growth patterns in Brachypodium distachyon using high-resolution time-lapse imaging. Pronounced changes in growth rate were observed under combined photocyles and thermocycles or with thermocycles alone. A considerably more rapid growth rate was observed at 28°C than 12°C, irrespective of the presence or absence of light. In spite of clear circadian clock regulated gene expression, plants exhibited no change in growth rate under conditions of constant light and temperature, and little or no effect under photocycles alone. Therefore, temperature appears to be the primary cue influencing observed oscillations in growth rate and not the circadian clock or photoreceptor activity. Furthermore, the size of the leaf meristem and final cell length did not change in response to changes in temperature. Therefore, the nearly five-fold difference in growth rate observed across thermocycles can be attributed to proportionate changes in the rate of cell division and expansion. A better understanding of the growth cues in B. distachyon will further our ability to model metabolism and biomass accumulation in grasses.
