Du Kang, Zhao Wenqing, Lv Zhiwei, Liu Lin, Ali Saif, Chen Binglin, Hu Wei, Zhou Zhiguo, Wang Youhua
College of Agriculture, Nanjing Agricultural University, Nanjing, China.
College of Agronomy and Biotechnology, Southwest University, Chongqing, China.
Physiol Plant. 2023 Sep-Oct;175(5):e14019. doi: 10.1111/ppl.14019.
In maize, young kernels that are less competitive and have poor sink activity often abort. Studies have indicated that such poor competitiveness depends, in part, on the regulation by auxin (IAA) and abscisic acid (ABA). However, the mechanisms for such effects remain unclear. We used pollination-blocking and hand-pollination treatments accompanied by multi-omics and physiological tests, to identify underlying mechanism by which IAA and ABA, along with sugar signaling affect kernel development. Results showed that preventing pollination of the primary ears reactivated kernels in the secondary ears and altered both sugar metabolism and hormone signaling pathways. This was accompanied by increased enzyme activities in carbon metabolism and concentrations of glucose and starch, as well as increased levels of IAA and decreased levels of ABA in the reactivated kernels. Positive and negative correlations were observed between IAA, ABA contents and cell wall invertase (CWIN) activity, and glucose contents, respectively. In vitro culture revealed that the expression of genes involved in glucose utilization was upregulated by IAA, but downregulated by ABA. IAA could promote the expression of ABA signaling genes ZmPP2C9 and ZmPP2C13 but downregulated the expression of Zmnced5, an ABA biosynthesis gene, and ZmSnRK2.10, which is involved in ABA signal transduction. However, these genes showed opposite trends when IAA transport was inhibited. To summarize, we suggest a regulatory model for how IAA inhibits ABA metabolism by promoting the smooth utilization of glucose in reactivated young kernels. Our findings highlight the importance of IAA in ABA signaling by regulating glucose production and transport in maize.
在玉米中，竞争力较弱且库活性较差的幼嫩籽粒常常会败育。研究表明，这种较差的竞争力部分取决于生长素（IAA）和脱落酸（ABA）的调控。然而，这种影响的机制仍不清楚。我们采用授粉阻断和人工授粉处理，并结合多组学和生理测试，以确定IAA、ABA以及糖信号影响籽粒发育的潜在机制。结果表明，阻止主穗授粉会重新激活次穗中的籽粒，并改变糖代谢和激素信号通路。这伴随着重新激活的籽粒中碳代谢酶活性增加、葡萄糖和淀粉浓度升高，以及IAA水平升高和ABA水平降低。分别观察到IAA、ABA含量与细胞壁转化酶（CWIN）活性以及葡萄糖含量之间存在正相关和负相关。体外培养表明，IAA上调参与葡萄糖利用的基因表达，而ABA则下调其表达。IAA可促进ABA信号基因ZmPP2C9和ZmPP2C13的表达，但下调ABA生物合成基因Zmnced5和参与ABA信号转导的ZmSnRK2.10的表达。然而，当IAA运输受到抑制时，这些基因呈现相反的趋势。综上所述，我们提出了一个关于IAA如何通过促进重新激活的幼嫩籽粒中葡萄糖的顺利利用来抑制ABA代谢的调控模型。我们的研究结果突出了IAA在通过调节玉米中葡萄糖的产生和运输来影响ABA信号传导方面的重要性。
