Abstract
Plant polyploids tend to have large leaves, but their formation mechanism has not yet been well explained. Therefore, daily transcriptomic differences between triploids and diploids from a synthetic Populus sect. Tacamahaca three times a day (i.e., 04:00, 09:00, and 21:00) were investigated using high-throughput RNA-seq analysis. In this study, we identified several transcription factors associated with giant leaves. The combined effects included the high expression of several transcription factors (WRKY, MYB, etc.) and hormone-related genes (e.g., activates auxin, cytokine, and brassinosteroid synthesis-related genes) that accelerate the synthesis and accumulation of endogenous hormones. High levels of growth hormones were maintained by reducing the genes’ expression of hormone metabolism and degradation. The coordination of hormones accumulated sufficient materials and energy for leaf growth and development. Thereby, cell division and growth were accelerated which enhanced the photosynthesis of leaves, and the increased accumulation of photosynthetic products led to giant triploid leaves. This study lays the foundation for revealing the molecular mechanisms in the formation of giant leaves in polyploids.
Highlights
Giant-sized leaves are an important phenotypic characteristic of plant polyploids [1,2,3]
We found that the differentially expressed genes between triploid and diploid leaves of poplar were concentrated in the transcription factors, hormone signal transduction, photosynthetic energy metabolism, and lignin and cellulose metabolism
Auxin and cytokinin synthesis were related to high expression of BR-related genes, inhibited the expression of BAS1, CKX7 and other plant hormone degradation genes, and modified the formation of the triploid leaf
Summary
Giant-sized leaves are an important phenotypic characteristic of plant polyploids [1,2,3]. Polyploids ligneous plants have a longer, wider leaf shape and larger leaf cells than diploids [6]. The giant leaves are formed by polyploidization, which increases the rate of cell elongation [7]. Triploid poplars have a larger leaf area and higher volume growth [8,9,10,11]. This is because the nature of giant leaves is closely related to the growth advantages of polyploids [12]
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