Abstract
Wizened buds are frequently observed in pear (Pyrus spp.) trees, which greatly reduces the yield. However, little is known about the mechanism of wizened bud formation. Here, we analyzed physiological and transcriptomic differences between normal buds and wizened buds of ‘710’ pear trees. The results indicated that the sorbitol and boron (B) contents, during bud differentiation, were significantly reduced in wizened buds. The microscopic observation and transcriptome analysis revealed that the collapse of the organ structure and cell wall loosening process may have a close relation with wizened bud formation. Moreover, reduced transcript levels of PpyMYB39.1 and its downstream genes (PpyHT1, PpyHT2, PpyPMEI1 and PpyPMEI2) were found in wizened buds. However, the transcript levels of pentose and glucuronate interconversion pathway genes (PpyPME3, PpyPL18.1, PpyPL18.2, PpyPG1 and PpyPG2) and the concentration of pectin-degradation-related enzymes were increased in wizened buds. Correspondingly, the pectin concentration was significantly reduced in wizened buds. Taken together, PpyMYB39.1 may promote pectin degradation and decrease carbohydrate transport by regulating its downstream genes and is supposed to play a vital role in the wizened bud formation resulting from the cell wall loosening process. Our study provides fundamental insights into wizened bud formation and strategies to reduce the wizened bud occurrence in pear trees.
Highlights
Pear (Pyrus spp.) is one of the major temperate fruit crops [1], which has grown widely with the global production of over 23.1 million tons in the year 2020 [2]
‘710’ buds sand with a hub shape; the bud scales were loosely surrounded by wizened buds pear plants
The concentration of pectin and the enzymes corresponding to these genes were significantly lower in wizened buds than in normal buds (Figure 7). These results suggested that the pectin degradation process was initiated after wizened bud occurrence
Summary
Pear (Pyrus spp.) is one of the major temperate fruit crops [1], which has grown widely with the global production of over 23.1 million tons in the year 2020 [2]. In China, pear is an economical fruit crop, and its yield is affected by developmental processes, especially bud germination [3,4]. The occurrence of wizened buds has been reported in many Rosaceae fruit trees, including pear [5], apple [8] and peach [9]. Boron (B) is involved in the cell wall development of bud meristem, and sugar alcohols act as the carbon source for the cell division of bud organs during bud differentiation [12,13,14]. Sorbitol, in addition to the energy source, plays an important role in reproductive development by regulating the expression of SDH genes [20,21]
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