改良玉米根部性状，培育高产、耐密品种

      玉米是中国最大种植面积的作物，在食用、饲用及工业原料领域都有很大的用途。玉米单产的提升对于我国粮食安全、消费升级、工业发展都具有重要的作用。一直以来，理想的玉米品种需要具备如下特征：高生物量和产量、高群体光合速率潜力、高密度种植下的耐倒伏和低空杆率、高籽粒灌浆速度、高千粒重以及对生物和非生物胁迫稳定的抗性。其中，根系发育对玉米产量影响巨大。最近，山东大学张举任教授团队系统研究了一个控制生长素在玉米根尖积累的基因，为改良玉米根部性状，培育高产玉米品种提供了方向。

      在很多植物中，PIN（PIN-FORMED）蛋白都具有调控生长素运输，影响根生长发育的功能。为了弄清楚玉米根发育的控制基因，研究人员在玉米自交系DH4866中克隆了拟南芥AtPIN1的4个同源基因ZmPIN1a、ZmPIN1b、ZmPIN1c、ZmPIN1d。其中超量表达ZmPIN1a导致了玉米侧根数量增加，从而形成了更加强大的根系。此外， ZmPIN1a超表达材料株高穗位也有一定程度的降低。这些表型都有利于玉米在密植条件下提高单株产量、抗逆性和抗倒性。进一步研究显示，产生这些表型的原因是生长素IAA从茎向根的运输增加，从而增加了根部碳水化合物的含量。
      玉米PIN类基因的功能研究和应用将有助于改良玉米根部性状，培育高产、耐密品种。
 Plant Biotechnology Journal, 23 JUN 2017
Enhancing auxin accumulation in maize root tips improves root growth and dwarfs plant height
Author
Zhaoxia Li, Xinrui Zhang, Yajie Zhao, Yujie Li, Guangfeng Zhang, Zhenghua Peng and Juren Zhang*
*: School of Life Science, Shandong University, China
Abstract
Maize is a globally important food, feed crop and raw material for the food and energy industry. Plant architecture optimization plays important roles in maize yield improvement. PIN-FORMED (PIN) proteins are important for regulating auxin spatiotemporal asymmetric distribution in multiple plant developmental processes. In this study, ZmPIN1a overexpression in maize increased the number of lateral roots and inhibited their elongation, forming a developed root system with longer seminal roots and denser lateral roots. ZmPIN1a overexpression reduced plant height, internode length and ear height. This modification of the maize phenotype increased the yield under high-density cultivation conditions, and the developed root system improved plant resistance to drought, lodging and a low-phosphate environment. IAA concentration, transport capacity determination and application of external IAA indicated that ZmPIN1a overexpression led to increased IAA transport from shoot to root. The increase in auxin in the root enabled the plant to allocate more carbohydrates to the roots, enhanced the growth of the root and improved plant resistance to environmental stress. These findings demonstrate that maize plant architecture can be improved by root breeding to create an ideal phenotype for further yield increases.