Xylem cell size regulation is a key adaptive response to water deficit in Eucalyptus grandis.

IF 3.5 2区 农林科学 Q1 FORESTRY
Rafael Keret, David M Drew, Paul N Hills
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引用次数: 0

Abstract

Future climatic scenarios forecast increasingly frequent droughts that will pose substantial consequences on tree mortality. In light of this, drought-tolerant eucalypts have been propagated; however, the severity of these conditions will invoke adaptive responses, impacting the commercially valuable wood properties. To determine what mechanisms govern the wood anatomical adaptive response, highly controlled drought experiments were conducted in Eucalyptus grandis W. Hill ex Maiden, with the tree physiology and transcriptome closely monitored. In response to water deficit, E. grandis displays an isohydric stomatal response to conserve water and enable stem growth to continue, albeit at a reduced rate. Maintaining gaseous exchange is likely a critical short-term response that drives the formation of hydraulically safer xylem. For instance, the development of significantly smaller fibers and vessels was found to increase cellular density, thereby promoting drought tolerance through improved functional redundancy, as well as implosion and cavitation resistance. The transcriptome was explored to identify the molecular mechanisms responsible for controlling xylem cell size during prolonged water deficit. Downregulation of genes associated with cell wall remodeling and the biosynthesis of cellulose, hemicellulose and pectin appeared to coincide with a reduction in cellular enlargement during drought. Furthermore, transcript levels of NAC and MYB transcription factors, vital for cell wall component biosynthesis, were reduced, while those linked to lignification increased. The upregulation of EgCAD and various peroxidases under water deficit did not correlate with an increased lignin composition. However, with the elevated cellular density, a higher lignin content per xylem cross-sectional area was observed, potentially enhancing hydraulic safety. These results support the requirement for higher density, drought-adapted wood as a long-term adaptive response in E. grandis, which is largely influenced by the isohydric stomatal response coupled with cellular expansion-related molecular processes.

木质部细胞大小调节是桉树对缺水的一个关键适应性反应。
根据未来气候预测,干旱会越来越频繁,对树木的死亡率造成严重影响。有鉴于此,耐旱的桉树得到了繁殖,然而,这些条件的严重程度将引起适应性反应,影响具有商业价值的木材特性。为了确定木材解剖学适应性反应的机制,我们在桉树中进行了高度受控的干旱实验,并对树木的生理机能和转录组进行了密切监测。在缺水情况下,桉树表现出等水气孔反应,以保存水分并使茎干继续生长,尽管生长速度有所降低。保持气体交换很可能是一种关键的短期反应,它能推动形成水力较弱的木质部。例如,研究发现,纤维和血管明显变小可增加细胞密度,从而通过改善功能冗余以及抗内爆和抗气蚀能力来提高耐旱性。研究人员对转录组进行了探索,以确定在长期缺水期间控制木质部细胞大小的分子机制。与细胞壁重塑以及纤维素、半纤维素和果胶的生物合成相关的基因下调似乎与干旱期间细胞增大的减少相吻合。此外,对细胞壁成分生物合成至关重要的 NAC 和 MYB 转录因子的转录水平降低了,而与木质化有关的转录因子的转录水平却升高了。缺水情况下 EgCAD 和各种过氧化物酶的上调与木质素成分的增加无关。不过,随着细胞密度的增加,木质部横截面积的木质素含量也增加了,这可能会提高水力安全性。这些结果支持了对更高密度、适应干旱的木材的要求,这是大叶黄杨的一种长期适应性反应,主要受等水气孔反应和细胞膨胀相关分子过程的影响。
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来源期刊
Tree physiology
Tree physiology 农林科学-林学
CiteScore
7.10
自引率
7.50%
发文量
133
审稿时长
1 months
期刊介绍: Tree Physiology promotes research in a framework of hierarchically organized systems, measuring insight by the ability to link adjacent layers: thus, investigated tree physiology phenomenon should seek mechanistic explanation in finer-scale phenomena as well as seek significance in larger scale phenomena (Passioura 1979). A phenomenon not linked downscale is merely descriptive; an observation not linked upscale, might be trivial. Physiologists often refer qualitatively to processes at finer or coarser scale than the scale of their observation, and studies formally directed at three, or even two adjacent scales are rare. To emphasize the importance of relating mechanisms to coarser scale function, Tree Physiology will highlight papers doing so particularly well as feature papers.
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