Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA.
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA; College of Agronomy, State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong 271018, China.
Gene. 2014 Jul 1;544(1):41-8. doi: 10.1016/j.gene.2014.04.038. Epub 2014 Apr 22.
The mitochondrial genomes of flowering plants exist both as a "master circle" chromosome and as numerous subgenomic sublimons that are generated by intramolecular recombination. Differential stability or replication of these sublimons allows individual mitochondrial gene copy numbers to vary independently between different cell types and developmental stages. Our objective was to determine the relationship between mitochondrial gene copy number and transcript abundance in the elongating fiber cells of Upland cotton (Gossypium hirsutum L.). We compared RNA and DNA from cotton fiber cells at five developmental time points from early elongation through secondary cell wall thickening from the Ligon-lintless 2 (Li2) short fiber mutant and its wild type near isogenic line (NIL) DP5690. Mitochondrial gene copy number decreased from 3 to 8-DPA in the developing cotton fiber cells while transcript levels remained low. As secondary cell wall biosynthesis began in developing fibers, the expression levels and copy numbers of mitochondrial genes involved in energy production and respiration were up-regulated in wild type cotton DP5690. However, the short fiber mutant Li2, failed to increase expression of these genes, which include three subunits of ATP synthase, atp1, atp8 and atp9 and two cytochrome genes cox1 and cob. At the same time, Li2 failed to increase the copy numbers of these highly expressed genes. Surprisingly, we found that when mitochondrial genes were highly transcribed, they also had very high copy numbers. This observation suggests that in developing cotton fibers, increased mitochondrial sublimon replication may support increases in gene transcription.
植物的线粒体基因组既存在于“主环”染色体中，也存在于由分子内重组产生的众多亚基因组亚隆中。这些亚隆的稳定性或复制的差异允许个体线粒体基因拷贝数在不同的细胞类型和发育阶段之间独立变化。我们的目的是确定线粒体基因拷贝数与陆地棉（Gossypium hirsutum L.）伸长纤维细胞中转录物丰度之间的关系。我们比较了来自 Ligon-lintless 2（Li2）短纤维突变体及其野生型近等基因系（NIL）DP5690 的棉花纤维细胞在五个发育时间点（从早期伸长到次生细胞壁加厚）的 RNA 和 DNA。在发育中的棉花纤维细胞中，线粒体基因拷贝数从 3 到 8-DPA 下降，而转录水平仍然很低。随着次生细胞壁生物合成在发育纤维中开始，参与能量产生和呼吸的线粒体基因的表达水平和拷贝数在野生型棉花 DP5690 中上调。然而，短纤维突变体 Li2 未能上调这些基因的表达，这些基因包括 ATP 合酶的三个亚基 atp1、atp8 和 atp9 以及两个细胞色素基因 cox1 和 cob。同时，Li2 未能增加这些高表达基因的拷贝数。令人惊讶的是，我们发现当线粒体基因转录水平很高时，它们的拷贝数也非常高。这一观察结果表明，在发育中的棉花纤维中，增加的线粒体亚隆复制可能支持基因转录的增加。
