Isoprene enhances leaf cytokinin metabolism and induces early senescence

第一作者：Kaidala Ganesha Srikanta Dani

第一单位：第一单位：意大利国家研究委员会可持续植物保护研究所

第一通讯：Francesco Loreto

 Abstract 

背景回顾：Isoprene, a major biogenic volatile hydrocarbon of climate-relevance, indisputably mitigates abiotic stresses in emitting plants. 

提出问题：However functional relevance of constitutive isoprene emission in unstressed plants remains contested. 

研究基础：Isoprene and cytokinins (CKs) are synthesised from a common substrate and pathway in chloroplasts. It was postulated that isoprene emission may affect CK-metabolism. 

研究内容：Using transgenic isoprene-emitting (IE) Arabidopsis and isoprene non-emitting (NE) RNAi grey poplars (paired with respective NE and IE genotypes), the life of individual IE and NE leaves from emergence to abscission was followed under stress-free conditions. 

研究方法：We monitored plant growth rate, above-ground developmental phenotype, modelled leaf photosynthetic energy status, quantified the abundance of leaf CKs, analyzed Arabidopsis and poplar leaf transcriptomes by RNA-sequencing in presence and absence of isoprene during leaf senescence. 

结果1-异戊二烯-CKs：Isoprene emission by unstressed leaves enhanced the abundance of CKs (isopentenyl adenine and its precursor) by >200%, significantly upregulated genes coding for CK-synthesis, CK-signaling and CK-degradation, hastened plant development, increased chloroplast metabolic rate, altered photosynthetic energy status, induced early leaf senescence in both Arabidopsis and poplar. 

结果2：IE leaves senesced sooner even in decapitated poplars where source-sink relationships and hormone homeostasis were perturbed. 

结果3：Constitutive isoprene emission significantly accelerates CK-led leaf and organismal development and induces early senescence independent of growth constraints. 

结论：Isoprene emission provides an early-riser evolutionary advantage and shortens lifecycle duration to assist rapid diversification in unstressed emitters.

 摘 要 

异戊二烯是一种与气候相关的主要生物挥发性碳氢化合物，对于挥发异戊二烯的植物来说可以帮助缓解所遭遇的非生物胁迫。然而，非胁迫环境条件下植物中组成型的异戊二烯释放，其是否具备功能仍然存在争议。异戊二烯和细胞分裂素（CKs）是在叶绿体中，由共同的底物和途径所合成的。异戊二烯释放可能会影响CK代谢。作者通过利用转基因的异戊二烯释放型（IE）和野生型（异戊二烯非释放型NE）拟南芥以及转基因异戊二烯非释放型（NE）RNA干扰株系和野生型（异戊二烯释放型IE）灰杨，在无胁迫条件下跟踪观察了各自物种中IE和NE的叶片从形成到脱落的寿命。作者监测了植物生长速率、地上部发育表型、模拟叶片光合能量状态、定量叶片CK的丰度，并在利用RNA-seq分析了有无异戊二烯的情况下，拟南芥和灰杨叶片在衰老过程中的转录图谱。非胁迫条件下，拟南芥和灰杨中叶片所释放的异戊二烯使得CK（异戊烯基腺嘌呤及其前体）的丰度增加了200%以上，显著上调了CK合成、信号转导以及降解相关基因的表达，加速了植物的发育，增加了叶绿体代谢率，改变了光合能量状态，诱导了叶片提前衰老。在断顶的杨树中，源库关系和激素稳态受到干扰，但IE杨树的叶片也会提前衰老。组成型异戊二烯释放显著加速了CK诱导的叶片和组织发育，并独立于生长限制，诱导提前衰老。异戊二烯释放提供了一个“早起者”演化优势，缩短了生命周期，有助于无胁迫释放的快速多样化。