Regulation of assimilate import into sink organs: update on molecular drivers of sink strength.
Regulation of assimilate import into sink organs: update on molecular drivers of sink strength.
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DOI：
10.3389/fpls.2013.00177
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发表时间：
2013
影响因子：
5.6
通讯作者：
Braun DM
中科院分区：
文献类型：
--
作者：
Bihmidine S;Hunter CT 3rd;Johns CE;Koch KE;Braun DM
最近的发展改变了我们对决定汇强度的分子机制的看法，库强度在这里被定义为非光合作用结构竞争光同化物进口的能力。我们回顾了来自不同系统的新发现，包括茎、种子、花和果实。一个重要的进展是确定了在细胞水平上糖的积累和平衡中起主要作用的新的转运体和促进剂。在不同的系统中，每一种方式发挥作用的具体位置各不相同。例如，甘蔗和甜高粱茎都积累了高水平的蔗糖，但可能通过不同的途径做到这一点。这种区别是利用转运蛋白基因有针对性地操纵汇强度的策略的核心，并表明了特定系统分析的重要性。另一个重大进展是确认深度低氧是谷物正常发育的一个特征。这意味着胚乳中库强度的分子驱动因素在非常低的氧气水平下工作，并且在与之前假设的代谢条件完全不同的情况下工作。然而，通过上调淀粉生物合成的基因，谷物的库容量得到了成功的增强。此外，蔗糖酶(InVS)不仅在蔗糖代谢中扮演双重角色，而且在调节细胞周期和细胞分裂程序的己糖信号的产生中扮演双重角色，这也增强了我们对库强度的理解。INV对细胞扩张和分裂的这些贡献被证明对从花到果实的幼库的建立至关重要。由于INV基因本身是对糖反应的“盛宴基因”，当同化物丰富时，它们可以调节前馈增强的库强度。因此，在关键情况下获得了更高的总体生产率和产量，这表明，随着我们发现驱动不同系统中下沉强度的详细分子机制，可能会实现更广泛的增强。
Recent developments have altered our view of molecular mechanisms that determine sink strength, defined here as the capacity of non-photosynthetic structures to compete for import of photoassimilates. We review new findings from diverse systems, including stems, seeds, flowers, and fruits. An important advance has been the identification of new transporters and facilitators with major roles in the accumulation and equilibration of sugars at a cellular level. Exactly where each exerts its effect varies among systems. Sugarcane and sweet sorghum stems, for example, both accumulate high levels of sucrose, but may do so via different paths. The distinction is central to strategies for targeted manipulation of sink strength using transporter genes, and shows the importance of system-specific analyses. Another major advance has been the identification of deep hypoxia as a feature of normal grain development. This means that molecular drivers of sink strength in endosperm operate in very low oxygen levels, and under metabolic conditions quite different than previously assumed. Successful enhancement of sink strength has nonetheless been achieved in grains by up-regulating genes for starch biosynthesis. Additionally, our understanding of sink strength is enhanced by awareness of the dual roles played by invertases (INVs), not only in sucrose metabolism, but also in production of the hexose sugar signals that regulate cell cycle and cell division programs. These contributions of INV to cell expansion and division prove to be vital for establishment of young sinks ranging from flowers to fruit. Since INV genes are themselves sugar-responsive “feast genes,” they can mediate a feed-forward enhancement of sink strength when assimilates are abundant. Greater overall productivity and yield have thus been attained in key instances, indicating that even broader enhancements may be achievable as we discover the detailed molecular mechanisms that drive sink strength in diverse systems.
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