短T-cycle下萵苣品種生長性狀差異與生物時鐘核心基因表現

Abstract

在植物工廠與設施農業的發展中，透過調控光環境以提升能源效率是關鍵課題。雖然縮短T-cycle具備加速作物週轉與節省電力之潛力，但依據時間農法(chronoculture)之觀點，環境週期仍須考量植物內生時鐘的運作特性。作物能否適應此類非標準光環境，取決於其內在節律與環境週期是否達成共振。本研究旨在鑑定萵苣(Lactuca sativa L.)之生物時鐘核心基因，並探討不同品種在短T-cycle下的生長適應性與分子運作機制。本研究首先利用生物資訊學方法，在萵苣基因組中鑑定了LsLHY、LsPRR7與LsELF3等核心時鐘基因。後續對30個萵苣品種進行生長篩選試驗，比較其在正常24小時週期(12小時光照/12小時黑暗, T24)與縮短之18小時週期(9小時光照/9小時黑暗, T18)下的表現。結果顯示，品種間對T-cycle的反應存在顯著差異。試驗發現，非共振壓力削弱了作物的生理恆定性與環境緩衝能力，使其對微環境異質性過度敏感，導致微環境效應被放大，掩蓋了T-cycle處理成為影響產量的主導因子。分子層次的表現分析進一步釐清了品種間適應策略的差異。內生週期接近24小時的‘吉林蘿蔓’，在T18短週期壓力下，其晚間複合體核心基因LsELF3節律崩潰，導致下游生長抑制功能失效，進而誘發了葉片異常擴展的形態適應。此發現展現了非共振T-cycle應用於「形態工程(morphological engineering)」的潛力。反之，‘陽光甜脆’被證實為具備短內生週期(τ ≈ 21 h)的特殊種原，其在T24下表現出明顯的相位提早與振幅抑制，但在T18環境下因相位吻合而使LsELF3節律獲得重塑。本研究證實了萵苣品種間存在內生週期的自然變異，且「晝夜節律共振」是決定作物在設施環境中生長表現與環境敏感度的關鍵。研究結果建議，在實踐節能短T-cycle的生產模式時，應篩選具備相應內生週期的品種，或利用基因編輯技術針對關鍵時鐘基因進行改良，以實現精準且高效的設施栽培。

In the development of plant factories and controlled environment agriculture (CEA), enhancing energy efficiency through the regulation of light environments is a critical issue. While shortening the T-cycle offers the potential to accelerate crop turnover and conserve electricity, the principles of chronoculture dictate that the environmental cycle must still account for the operational characteristics of the plant's endogenous circadian clock. The ability of crops to adapt to such non-standard light environments depends on whether resonance is achieved between their endogenous rhythms and the environmental cycle. This study aims to identify core circadian clock genes in lettuce (Lactuca sativa L.) and investigate the growth adaptability and molecular mechanisms of different cultivars under short T-cycles. Using bioinformatic approaches, this study first identified core clock genes, including LsLHY, LsPRR7, and LsELF3, within the lettuce genome. Subsequently, a growth screening experiment was conducted on 30 lettuce cultivars to compare their performance under a normal 24-hour T-cycle (12 h light/12 h dark, T24) and a shortened 18-hour T-cycle (9 h light/9 h dark, T18). The results revealed significant variations in responses to T-cycles among the cultivars. Experimental observations indicated that non-resonant stress compromised the crops' physiological homeostasis and environmental buffering capacity, rendering them overly sensitive to micro-environmental heterogeneity. Consequently, micro-environmental effects were amplified, overshadowing the T-cycle treatment as the dominant factor influencing yield. Gene expression analysis at the molecular level further elucidated the differences in adaptive strategies among cultivars. In ‘Jilin Romaine’, which possesses an endogenous period close to 24 hours, the rhythm of the Evening Complex core gene LsELF3 collapsed under T18 short-cycle stress. This disruption led to the failure of downstream growth inhibition functions, thereby inducing a morphological adaptation characterized by abnormal leaf expansion. This finding highlights the potential of utilizing non-resonant T-cycles for "morphological engineering." Conversely, ‘Sunshine Crisp’ was verified as a unique germplasm with a short endogenous period (τ ≈ 21 h). While it exhibited distinct phase advancement and amplitude suppression under T24 conditions, its LsELF3 rhythm was successfully reshaped under the T18 environment due to phase alignment. In conclusion, this study confirms the existence of natural variation in endogenous periods among lettuce cultivars and establishes that "circadian resonance" is a critical determinant of crop growth performance and environmental sensitivity in controlled environments. The findings suggest that to implement energy-saving short T-cycle production models, strategies should include screening for varieties with matching endogenous periods or utilizing gene editing technologies to modify key clock genes, thereby achieving precise and efficient controlled environment cultivation.