Starch accumulation is important during com development. ADP-glucose pyrophosphorylase (AGPase) is the rate-limiting enzyme in starch synthesis. AGPL is the large subunit of AGPase. Here, we isolated and characterized the large subunit of AGPase gene GhAGPL1 in gladiolus (Gladiolus hybridus). GhAGPL1 was highly expressed in sink organs (cormels and corms). The expression of GhAGPL1 was induced by glucose, sucrose, and mannitol, and it was repressed by abscisic acid (ABA). Overexpression of GhAGPL1 in the arabidopsis (Arabidopsis thaliana) apl1 mutant resulted in complementation of AGPase activity and thus starch synthesis. Silencing GhAGPL1 in gladiolus decreased the transcript level of GhAGPL1 and GhSus, and resulted in the reduction of AGPase activity and starch content in gladiolus corm and cormel. Meanwhile, sucrose content was higher in GhAGPL1-silenced corm. Surprisingly, silencing GhAGPL1 in gladiolus produced smaller corms and fewer number of cormels. Overall, GhAGPL1 contributed to the quality and quantity of gladiolus corms and cormels.
Shanshan Seng, Jian Wu, Jiahui Liang, Fengqin Zhang, Qiuyan Yang, Junna He and Mingfang Yi
Jehanzeb Khan, Yubin Yang, Qiang Fu, Weiqiang Shao, Jianke Wang, Li Shen, Yan Huai, Guy Kateta Malangisha, Abid Ali, Ahmed Mahmoud, Yi Lin, Yongyuan Ren, Jinghua Yang, Zhongyuan Hu and Mingfang Zhang
Watermelon (Citrullus lanatus) is an important horticultural crop that is sensitive to heavy metals such as lead (Pb) in polluted water or soil. However, there are no available data regarding Pb tolerance phenotyping in watermelon. Watermelon seedlings were exposed to various Pb doses (0, 20, 40, 60, 80 µm·L–1 Pb) for 14 days, after which 20 µm Pb was identified as the optimal treatment for lead tolerance analysis in watermelon because it caused significant symptoms (leaf chlorosis, stubby and yellow roots) but little damage to seedlings. Subsequently, the Pb responses were analyzed in eight watermelon varieties (V1–V8), and membership function analysis was used to determine a single Pb tolerance index. Of the eight watermelon varieties, V4 and V7 were ranked the most Pb tolerant; V1, V2, V5, and V6 were moderately Pb tolerant; and V3 and V8 were the most Pb-sensitive varieties. Compared with most Pb-sensitive varieties (V3 and V8), the most Pb-tolerant varieties (V4 and V7) maintained high antioxidant activity, and had lower malondialdehyde (MDA) and total soluble protein (TSP) contents. In addition, carotenoid and chlorophyll (both a and b) contents were stimulated and inhibited, respectively, in leaves of high-Pb translocation varieties (V4 and V8). Principal component analysis (PCA) revealed relative root length as an indicator of Pb tolerance because it correlated significantly with shoot growth. These results provide useful insight into the mechanism of Pb tolerance in cucurbit crops, as well as information regarding the breeding of watermelon with enhanced tolerance to this heavy metal (Pb).