Abstract
Pear is one of the most important economic fruits worldwide. The productivity is often negatively affected by drought disaster, but the effects and adaptive mechanism of pear in response to drought stress has not been well understood at the gene transcription levels. Using Illumina HiSeq 2500, the transcriptome from 'Yulu Xiang' Pear leaves were sequenced and analyzed to evaluate the effects of long-term drought stress on the expression of genes in different biosynthetic pathways. Results showed that long-term drought stress weakened antioxidant systematization and impaired the synthesis of photosynthetic pigment in 'Yulu Xiang' Pear leaves. The reduced light utilization and photosynthetic productivity finally resulted in the inhibited fruit development. The transcriptome survey and expression analysis identified 2,207 differentially expressed genes (DEGs) which were summarized into the 30 main functional categories. DEGs analysis showed that the enzyme genes involved in phenylpropanoid biosynthesis under drought stress were up-regulated, and the promoted process of phenylpropanoid synthesis may be beneficial to reduce the transpiration rate and increase water use efficiency of 'Yulu Xiang' Pear leaves. Up-regulated malate dehydrogenase expression were also observed in drought stress groups, and the activated soluble sugar biosynthesis could be helpful to promote osmotic regulation and increase antioxidant capacity to enhance drought resistance of leaves. The mRNA expression of enzyme genes associated with hormones including ethylene, abscisic acid, and gibberellin were higher in drought stress groups than that in control, indicating a promoted cell proliferation under drought stress. Long-term drought stress significantly decreased photosynthetic productivity, and negatively affected development of 'Yulu Xiang' Pear. Transcriptome survey and expression analysis reveals that the inhibited photosynthesis could be closely related with drought-induced lignification and hormones synthesis, and the present dataset can provide more valuable information to analyze the function of drought stress-related genes improving plant drought tolerance.
Highlights
IntroductionPear is one of the most widely grown fruit species worldwide, but the unpredictable reduction from adverse weather (such as drought disaster) is an urgent problem [1, 2]
Pear is one of the most widely grown fruit species worldwide, but the unpredictable reduction from adverse weather is an urgent problem [1, 2]
The nutrients accumulation in fruit greatly depends on the transportation from photosynthesis products, and it was quite possible that the reduced fruit soluble solids may be resulted from the impaired photosynthesis in leaves induced by drought stress
Summary
Pear is one of the most widely grown fruit species worldwide, but the unpredictable reduction from adverse weather (such as drought disaster) is an urgent problem [1, 2]. Studies found that water deficiency was second only to the shortage of illumination causing the reduced photosynthetic rate [6, 7]. Water deficiency may promote transpiration by increasing temperature of plant leaves, and the contradiction between supply of water and demand of plant body may result in the reduced photosynthetic rate. Maes et al [8] reported that the water potential, relative water content, leaf area, stomatal conductance of fruit seedlings leaves under drought stress was reduced, which caused the decline of leaf photosynthetic rate. Down-regulated stomatal conductance induced by drought stress inhibited the entry of carbon dioxide from the external environment into leaves, and increased resistance of mesophyll cells, and weakened carboxylase activity [9]
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