The transcription factor PbrbZIP52 positively affects pear pollen tube longevity by promoting callose synthesis

Abstract

In pear (Pyrus bretschneideri), pollen tube growth is critical for the double fertilization associated with seed setting, which in turn affects fruit yield. The normal deposition of callose mediates the polar growth of pollen tubes. However, the mechanism regulating callose synthesis in pollen tubes remains relatively uncharacterized. In this study, we revealed that the typical pear pollen tube lifecycle has a semi-growth duration (GD50) of 16.16 h under in vitro culture conditions. Moreover, callose plugs were deposited throughout the pollen tube lifecycle. The formation of callose plugs was inhibited by 2-deoxy-D-glucose, which also accelerated the senescence of pear pollen tubes. Additionally, PbrCalS1B.1, which encodes a plasma membrane-localized callose synthase, was expressed specifically in pollen tubes and restored the fertility of the Arabidopsis (Arabidopsis thaliana) cals5 mutant in which callose synthesis is inhibited. However, this restoration of fertility was impaired by the transient silencing of PbrCalS1B.1, which restricts callose plug formation and shortens the pear pollen tube lifecycle. More specifically, PbrbZIP52 regulated PbrCalS1B.1 transcription by binding to promoter A-box elements to maintain the periodic formation of callose plugs and normal pollen tube growth, ultimately leading to double fertilization. This study confirmed that PbrbZIP52 positively affects pear pollen tube longevity by promoting callose synthesis. This finding may be useful for breeding high-yielding pear cultivars and stabilizing fruit setting in commercial orchards.

Morphological Study on the Differentiation of Flower Buds and the Embryological Stages of Male and Female Floral Organs in Lespedeza davurica (Laxm.) Schindl. cv. JinNong (Fabaceae)

“…It plays a crucial role in various stages of plant growth and development. It can reduce the cell turgor pressure caused by the elongation of the top of the pollen tube, and it can also increase the ductility of the pollen tube tip to maintain the growth of polar pollen tubes [ 40 ]. In addition, callose is deposited at the site of pathogen invasion, between the plasma membrane and the cell wall in plasmodesmata and other plant tissues, to slow down the invasion and spread of pathogens [ 41 ].…”

Transcriptomic Insight into the Pollen Tube Growth of Olea europaea L. subsp. europaea Reveals Reprogramming and Pollen-Specific Genes Including New Transcription Factors

“…Flavonoids participate in successful pollen germination by increasing the phenylpropanoid pathways [ 12 ], ROS scavenging and maintenance of turgor and normal morphology [ 13 , 14 ]. Morphology of PTs depends on ions and water filling the new volume [ 15 , 16 ] and the cell wall that sustains turgor pressure [ 17 , 18 ].…”