Abstract
The branching system of higher plants plays a very important role in plant morphogenesis, and the number of branches can directly affect crop yield and the ornamental value of plants. It is a complicated development process involving complex molecular mechanisms. The ‘Cailinghong’ variety of Salvia splendens is characterized by its great branching ability with the ability to grow into a spherical form naturally, without pinching. To gain insight into the molecular events during the branching development of S. splendens, suppressive subtractive hybridization (SSH) technology was used to screen differentially expressed genes between the erect plant type (strain 35) and the spherical plant type (‘Cailinghong’). In total, 96 and 116 unigenes were annotated. Four and eight unigenes up-regulated in ‘Cailinghong’ and strain 35, respectively, were associated with plant hormone anabolism and signal transduction, suggesting that they participate in the branching process. One of these genes, phytoene synthase (PSY), is a precursor of the new plant hormone group strigolactones. Using the PSY fragment (192 bp) as a template, the cDNA sequence of PSY in S. splendens was cloned and named SsPSY. A relative expression analysis and transgenic test results indicated that SsPSY plays an important role in lateral branch development in ‘Cailinghong’. These results provide new insight into the molecular mechanisms underlying branching in S. splendens.
Highlights
MethodsThe ‘Cailinghong’ variety and strain 35 breeds by our research group were used as test materials
Resulting from the development and expansion of the terminal bud and axillary bud, branching is a complicated developmental trait in plants
Plant branching is controlled by the coordination of plant hormones; the unigenes related to hormone synthesis and signal transduction that were up-regulated in ‘Cailinghong’ or strain 35 may contribute to the unique branching pattern found in ‘Cailinghong’
Summary
The ‘Cailinghong’ variety and strain 35 breeds by our research group were used as test materials. Seeds of the tested varieties were planted in a greenhouse. After about 80 days of sowing, elongation of the primary lateral branch of the seedling began, and the top bud of the primary lateral branch at the second or third nodes of the tested varieties was obtained as test materials for SSH library construction and the cloning of SsPSY. 2.2 Morphological Characteristics of Strain 35 and ‘Cailinghong’. The tested varieties were grown in a greenhouse under a temperature of 25°C and 14 h of light a day. The morphology, plant height, and length of each branch were observed and measured regularly after sowing for 3 months.
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