Wouters Marlies, Corneillie Sander, Dewitte Angelo, Van Doorsselaere Jan, Van den Bulcke Jan, Van Acker Joris, Vanholme Bartel, Boerjan Wout
Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.
VIB Center for Plant Systems Biology, Ghent, Belgium.
Front Plant Sci. 2022 Sep 9;13:995402. doi: 10.3389/fpls.2022.995402. eCollection 2022.
The potential of whole genome duplication to increase plant biomass yield is well-known. In Arabidopsis tetraploids, an increase in biomass yield was accompanied by a reduction in lignin content and, as a result, a higher saccharification efficiency was achieved compared with diploid controls. Here, we evaluated whether the results obtained in Arabidopsis could be translated into poplar and whether the enhanced saccharification yield upon alkaline pretreatment of hairpin-downregulated () transgenic poplar could be further improved upon a whole genome duplication. Using a colchicine treatment, wild-type (WT) x cv. INRA 717-1B4, a commonly used model clone in tree biotechnology research, and tetraploids were generated and grown in the greenhouse. In parallel, WT tetraploid poplars were grown in the field. In contrast to Arabidopsis, a whole genome duplication of poplar had a negative impact on the biomass yield of both greenhouse- and field-grown trees. Strikingly, field-grown WT tetraploids developed a brittle apex phenotype, i.e., their tip broke off just below the apex. In addition, the chromosome doubling altered the biomass composition of field-grown, but not of greenhouse-grown tetraploid poplars. More specifically, the lignin content of field-grown tetraploid poplars was increased at the expense of matrix polysaccharides. This increase in lignin deposition in biomass is likely the cause of the observed brittle apex phenotype, though no major differences in stem anatomy or in mechanical properties could be found between di- and tetraploid WT poplars grown in the field. Finally, without biomass pretreatment, the saccharification efficiency of greenhouse- and field-grown WT diploids was not different from that of tetraploids, whereas that of greenhouse-grown tetraploids was higher than that of greenhouse-grown diploids. Upon alkaline pretreatment, the saccharification yield of diploids was similar to that of tetraploids for all genotypes and growth conditions tested. This study showed that a whole genome duplication in hybrid WT and poplar did neither result in further improvements in biomass yield, nor in improved biomass composition and, hence, saccharification performance.
全基因组加倍提高植物生物量产量的潜力是众所周知的。在拟南芥四倍体中，生物量产量的增加伴随着木质素含量的降低，因此与二倍体对照相比，糖化效率更高。在这里，我们评估了在拟南芥中获得的结果是否可以转化到杨树中，以及在发夹下调（）转基因杨树进行碱性预处理后提高的糖化产量在全基因组加倍后是否可以进一步提高。使用秋水仙碱处理，产生了野生型（WT）× cv. INRA 717 - 1B4（树木生物技术研究中常用的模型克隆）的四倍体，并在温室中生长。同时，WT四倍体杨树在田间生长。与拟南芥不同，杨树的全基因组加倍对温室和田间生长树木的生物量产量都有负面影响。引人注目的是，田间生长的WT四倍体出现了脆尖表型，即它们的顶端在顶点下方刚好折断。此外，染色体加倍改变了田间生长的四倍体杨树的生物量组成，但没有改变温室生长的四倍体杨树的生物量组成。更具体地说，田间生长的四倍体杨树的木质素含量增加，而基质多糖减少。生物量中木质素沉积的这种增加可能是观察到的脆尖表型的原因，尽管生长在田间的二倍体和四倍体WT杨树在茎解剖结构或机械性能方面没有发现重大差异。最后，在没有生物量预处理的情况下，温室和田间生长的WT二倍体的糖化效率与四倍体没有差异，而温室生长的四倍体的糖化效率高于温室生长的二倍体。经过碱性预处理后，在所有测试的基因型和生长条件下，二倍体的糖化产量与四倍体相似。这项研究表明，杂交WT和杨树的全基因组加倍既没有导致生物量产量的进一步提高，也没有改善生物量组成，因此也没有提高糖化性能。
