Characterisation of the molecular and cellular mechanisms controlling lateral root emergence using an integrative-systems based approach

粮食安全是一个重大的全球性问题。迫切需要显著提高作物产量，以养活到2050年急剧增加的世界人口。我们的工业合作伙伴最近发现了一系列提高产量的农用化学品，通过促进根系生长和分支来提高作物产量。增加根枝（称为侧根）的数量增加了作物的水分吸收和营养获取，因此了解侧根发育的调节具有至关重要的农艺意义。侧根（LR）发育可分为2个不同的过程；(A)形成（即在主根中心深处形成新根）；(B)出苗（即在主根深处形成的新根在进入土壤之前需要穿过周围组织）。研究主要集中在研究LR地层。然而，最近的证据表明，LR的出现是根分支的一个重要检查点，受硝酸盐和磷酸盐等营养物质以及生长素等激素信号的调节。我们最近的研究表明，生长素起源于新的LR，作为一个局部信号，促进覆盖的细胞分离，使新的根出现。我们已经确定了大约560个由生长素调控引起侧根萌发的基因。生长素对LR发生的影响非常复杂，涉及大约560种不同的基因。为了帮助我们处理这种复杂性，我们将采用一种称为系统生物学的新方法，生物学家和数学家密切合作。这包括生成大量关于这些不同基因的实验信息，然后将其整合到一个数学模型中。生长素通过诱导许多不同细胞和组织的反应来调节LR的出现。因此，我们的模型不仅要包括基因列表的信息，还要考虑它们在许多不同的根细胞和组织中的行为。然后，我们需要通过设计实验来测试其准确预测实际结果的能力，从而确定我们的根模型有多现实。然后，该模型可以用于测试想法，并提供关于生长素如何在基因、细胞和组织水平上控制LR出现的新见解。建立这个知识库将使我们能够准确地确定促进根系生长的农用化学品是如何影响根系发育的。从这项研究中获得的知识将帮助科学家了解如何最好地控制根系生长和提高作物产量。

Food security is a major global issue. Significant improvements in crop yields are urgently required to feed the dramatically increasing world population by 2050. Our industrial partner has recently discovered a series of yield enhancing agrochemicals that increase crop yield by promoting root growth and branching. Increasing the number of root branches (termed lateral roots) increases the water uptake and acquisition of nutrients in crops and therefore understanding the regulation of lateral root development is therefore of vital agronomic importance. Lateral root (LR) development can be divided into 2 distinct processes; (A) formation (i.e. new roots forming deep within the centre of the main root); and (B) emergence (i.e. when new roots which form deep inside the main root need to push through the surrounding tissues before entering the soil). Research has focused largely on studying LR formation. However, recent evidence suggests that LR emergence is an important checkpoint for root branching which is regulated by nutrients such as nitrate and phosphate and hormone signals such as auxin. We have recently shown that auxin originating from new LR acts as a local signal that promotes overlying cells to separate, enabling new roots to emerge. We have identified ~560 genes that auxin regulates to cause lateral root emergence. The effect of auxin on LR emergence is very complicated and appears to involve about 560 different genes. To help us deal with this complexity, we will employ a new approach termed Systems Biology in which biologists and mathematicians work closely together. This involves generating a large body of experimental information about these different genes which is then integrated into a mathematical model. Auxin regulates LR emergence by inducing responses in many different cells and tissues. Our model therefore has to include information not just about a list of genes but also consider their behaviour in many different root cells and tissues. We then need to determine how realistic our root model is, by designing experiments to test its ability to accurately predict real results. The model can then be used to test ideas and provide new insight about how auxin controls LR emergence at the gene, cell and tissue level. Establishing this knowledge base will enable us to determine exactly how the root-growth-promoting agrochemicals affect LR development. The knowledge gained from this study will help scientists understand how best to manipulate root growth and enhance crop yield.