Leaf photosynthesis is the energy source of plant life activities. However, some macadamia varieties (Macadamia integrifolia) planted in southern China are prone to generate the etiolated leaves under the continuous high temperature in summer, which seriously affects the shoot growth and fruit production of macadamia trees. In order to explore the mechanism of photosynthetic energy generation in the etiolated leaves of macadamia, the genes related to photosynthetic energy metabolism were identified and screened in this study, based on the previously obtained transcriptome sequencing data from the leaves of HAES344 macadamia at different yellowing stages, and the expression changes of the key genes in photosynthetic energy metabolism were analyzed during leaf yellowing of HAES344 macadamia by qRT-PCR. 96 genes with differential expression in the etiolated leaves of HAES344 macadamia were identified to be related to energy metabolism according to KEGG functional annotation and enrichment analysis, and the number of the differentially expressed genes enriched in the oxidative phosphorylation pathway was the highest, followed by carbon fixation pathway, and the least genes were enriched in the antenna proteins. After screening (RPKM>0.5), a total of 43 genes related to photosynthetic energy metabolism were obtained. Among these genes, the expression level of 27 genes decreased significantly in the yellowed leaves, while the remaining 16 genes did the opposite. Through the qRT-PCR analysis of the relative expression level of key functional genes in the photosynthetic energy metabolism, the CAP10A gene encoding photosystem Ⅱ (PSⅡ) antenna protein, the ATPC and ATPF genes encoding ATPase subunit protein, the enzyme genes related to carbon assimilation (GAPA, GPD, At4g2652 and rbcL), the Os05g0200100 and CXXS1 genes encoding thioredoxin, and the TIC32 gene associated with plastid protein transmembrane transport showed a significant lower transcription level in the etiolated leaves of HAES344 macadamia compared with the normal leaves, while the SIR and APR3 genes related to sulfur metabolism and the PGR5, ndhB and ndhD genes mediating cyclic electron transfer did the opposite, which suggested that the greatly changed expression patterns of genes related to photosynthetic energy metabolism affected the production of photosynthetic energy in the macadamia yellowing leaves. The results of this study would provide a reference for further exploring the mechanism of photosynthetic energy metabolism-related genes in the etiolated leaves of macadamia.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |