Liao Shengjin, Zhang Ying, Wang Jinglu, Zhao Chunjiang, Ruan Yong-Ling, Guo Xinyu
Beijing Key Laboratory of Digital Plant, Research Center of Information Technology, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China.
National Watermelon and Melon Improvement Center, Beijing Academy of Agriculture and Forestry Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, China.
Front Plant Sci. 2022 Apr 7;13:847884. doi: 10.3389/fpls.2022.847884. eCollection 2022.
Endosperm cavity (EC) in maize grain reduces yield and causes grain breakage during mechanical harvesting, hence representing a major problem in the maize industry. Despite this, little is known regarding the biological processes governing EC formation. Here, we attempted to address this issue by (i) determining the spatial and temporal progression of EC in a non-invasive manner and (ii) identifying candidate genes that may be linked to the formation of EC by using a genome wide association study (GWAS). Visualization and measurement using X-ray micro-computed tomography established that EC first appeared at the central starch endosperm at about 12 days after pollination (DAP) and became enlarged thereafter. GWAS-based screening of a panel of 299 inbred lines with a wide range of EC size identified nine candidate genes that showed significant association with EC formation. Most of the candidate genes exhibited a decrease at 12 DAP, coinciding with the timing of EC appearance. Among them, was annotated as a member encoding a multidrug resistance-associated protein that has been shown in other studies to sequestrate toxic metabolites from the cytosol to the vacuole, thereby detoxifying the cellular environment. This, together with the reduced expression of in maize grains from 12 DAP, prompted us to propose that the low expression of 11 may block cellular detoxification in the maize endosperm cells, leading to cell death and ultimately the formation of EC.
玉米籽粒中的胚乳腔会降低产量，并在机械收获过程中导致籽粒破碎，因此是玉米产业中的一个主要问题。尽管如此，关于胚乳腔形成的生物学过程却知之甚少。在此，我们试图通过以下方式解决这个问题：（i）以非侵入性方式确定胚乳腔在空间和时间上的进展，以及（ii）通过全基因组关联研究（GWAS）鉴定可能与胚乳腔形成相关的候选基因。使用X射线微计算机断层扫描进行可视化和测量表明，胚乳腔在授粉后约12天首次出现在中央淀粉胚乳中，此后逐渐扩大。基于GWAS对299个具有广泛胚乳腔大小的自交系进行筛选，鉴定出9个与胚乳腔形成显著相关联的候选基因。大多数候选基因在授粉后12天表达量下降，这与胚乳腔出现的时间一致。其中，一个基因被注释为编码多药耐药相关蛋白的成员，其他研究表明该蛋白可将有毒代谢物从细胞质隔离到液泡中，从而使细胞环境解毒。这一点，再加上该基因在授粉后12天的玉米籽粒中表达量降低，促使我们提出该基因低表达可能会阻碍玉米胚乳细胞的细胞解毒作用，导致细胞死亡并最终形成胚乳腔。
