Wang Yi, Jia Bingyu, Ren Hongjian, Feng Zhen
College of Forestry, Key Laboratory of State Forestry Administration for Silviculture of the Lower Yellow River, Shandong Agricultural University, Tai'an, Shandong Province, China.
Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, China.
PeerJ. 2021 Dec 16;9:e12620. doi: 10.7717/peerj.12620. eCollection 2021.
Polyploidy plays an important role in plant breeding and has widespread effects on photosynthetic capacity. To determine the photosynthetic capacity of the tetraploid variety Miq. Xingwang', we compared the gas exchange parameters, chloroplast structure, chlorophyll contents, and chlorophyll fluorescence parameters between the tetraploid 'Xingwang' and the diploid 'S4'. To evaluate the effects of genome duplication on the photosynthetic capacity of 'Xingwang', the transcriptomes of the autotetraploid 'Xingwang' and the diploid 'S4' of were compared.
The ploidy of 'Xingwang' was identified by flow cytometry and the chromosome counting method. An LI-6800 portable photosynthesis system analyzer was used to assess the gas exchange parameters of the tetraploid variety 'Xingwang' and diploid variety 'S4' of . We used a BioMate 3S ultraviolet-visible spectrophotometer and portable modulated fluorometer to measure the chlorophyll contents and chlorophyll fluorescence parameters, respectively, of 'Xingwang' and 'S4'. Illumina high-throughput sequencing technology was used to identify the differences in the genes involved in the photosynthetic differences and determine their expression characteristics.
The single-cell DNA content and chromosome number of the tetraploid 'Xingwang' were twice those found in the normal diploid 'S4'. In terms of gas exchange parameters, the change in stomatal conductance, change in intercellular CO concentration, transpiration rate and net photosynthetic rate of 'Xingwang' were higher than those of the diploid 'S4'. The chlorophyll contents, the maximal photochemical efficiency of PSII and the potential photochemical efficiency of PSII in 'Xingwang' were higher than those of 'S4'. The chloroplasts of 'Xingwang' contained thicker thylakoid lamellae. By the use of Illumina sequencing technology, a total of 51,807 unigenes were obtained; they had an average length of 1,487 nt, and the average N50 was 2,034 nt. The lengths of most of the unigenes obtained ranged from 200-300 bp, with an average value of 5,262, followed by those longer than 3,000 bp, with an average value of 4,791. The data revealed numerous differences in gene expression between the two transcriptomes. In total, 24,221 differentially expressed genes were screened, and the percentage of differentially expressed genes was as high as 46.75% (24,224/51,807), of which 10,474 genes were upregulated and 13,747 genes were downregulated. We analyzed the key genes in the photosynthesis pathway and the porphyrin and chlorophyll metabolism pathway; the upregulation of HemB may promote an increase in the chlorophyll contents of 'Xingwang', and the upregulation of related genes in PSII and PSI may enhance the light harvesting of 'Xingwang', increasing its light energy conversion efficiency.
多倍体在植物育种中起着重要作用，并且对光合能力具有广泛影响。为了测定四倍体品种‘兴王’的光合能力，我们比较了四倍体‘兴王’和二倍体‘S4’之间的气体交换参数、叶绿体结构、叶绿素含量以及叶绿素荧光参数。为了评估基因组加倍对‘兴王’光合能力的影响，我们比较了同源四倍体‘兴王’和二倍体‘S4’的转录组。
通过流式细胞术和染色体计数法鉴定‘兴王’的倍性。使用LI-6800便携式光合作用系统分析仪评估四倍体品种‘兴王’和二倍体品种‘S4’的气体交换参数。我们分别使用BioMate 3S紫外可见分光光度计和便携式调制荧光仪测量‘兴王’和‘S4’的叶绿素含量和叶绿素荧光参数。利用Illumina高通量测序技术鉴定参与光合差异的基因差异，并确定它们的表达特征。
四倍体‘兴王’的单细胞DNA含量和染色体数目是正常二倍体‘S4’的两倍。在气体交换参数方面，‘兴王’的气孔导度变化、胞间CO₂浓度变化、蒸腾速率和净光合速率均高于二倍体‘S4’。‘兴王’的叶绿素含量、PSII的最大光化学效率和PSII的潜在光化学效率均高于‘S4’。‘兴王’的叶绿体含有较厚的类囊体片层。通过Illumina测序技术，共获得51,807个单基因；它们的平均长度为1,487 nt，平均N50为2,034 nt。所获得的大多数单基因长度在200 - 300 bp之间，平均值为5,262，其次是长度超过3,000 bp 的，平均值为4,791。数据揭示了两个转录组之间在基因表达上存在众多差异。总共筛选出24,221个差异表达基因，差异表达基因的比例高达46.75%（24,224/51,807），其中10,474个基因上调，13,747个基因下调。我们分析了光合作用途径以及卟啉和叶绿素代谢途径中的关键基因；HemB的上调可能促进‘兴王’叶绿素含量的增加，PSII和PSI中相关基因的上调可能增强‘兴王’的光能捕获，提高其光能转换效率。
