Plant Cell Tissue and Organ Culture | 2021
Transcriptomic analyses reveal potential mechanisms of premature senescence in hexaploid Populus
Abstract
The important role of polyploidy in plant evolution is widely recognized. However, many questions concerning how polyploidy affects the plant phenotype remain unexplored. To elucidate the phenotypic and molecular effects of polyploidization, we obtained hexaploids by applying colchicine to a triploid clone (Populus tomentosa\u2009×\u2009P. bolleana)\u2009×\u2009(P. alba\u2009×\u2009P. glandulosa). The highest hexaploid induction rate (3.57%) resulted from a 3-day pre-culture treatment followed by treatment with colchicine by immersing the explant in 100\xa0mg\xa0l−1 colchicine for 96\xa0h. Reduction of photosynthesis and chloroplast degradation was observed in leaves of the hexaploid Populus which is an indication of early senescence. To investigate the gene expression underlying how polyploidization causes premature senescence, we compared the transcriptomes of the seventeenth leaf between hexaploid and triploid Populus; the leaf position was determined on the basis of preliminary experiments. 16,403 differentially expressed genes (DEGs) were identified between the hexaploids and the triploids. Based on the transcription information, several genes involved in the circadian rhythm and redox status may play important roles in premature senescence caused by polyploidization. Additionally, the MYB, AP2/EREBP, bHLH, NAC and WRKY transcription factors (TFs) may be more important than other TFs in the premature senescence of hexaploid Populus. The transcriptome results were consistent with those of quantitative real-time polymerase chain reaction (qRT-PCR), implying credibility. This study provides insights into the molecular mechanisms of the effects of polyploidization on phenotypic variation, which may be useful for the genetic improvement of polyploid breeding. The leaf transcriptome analysis suggest that genes involved in the circadian rhythm and redox status and several TF families may play a vital role in the premature senescence of hexaploid Populus.