State Ministry of Education Key Laboratory of Integrated Management of Crop Pathogens and Insect Pests, Nanjing Agricultural University, Jiangsu, 210095, China.
J Biosci. 2014 Mar;39(1):127-37. doi: 10.1007/s12038-013-9408-6.
Hpa1 is a harpin protein produced by Xanthomonas oryzae, an important bacterial pathogen of rice, and has the growth-promoting activity in plants. To understand the molecular basis for the function of Hpa1, we generated an inactive variant protein, Hpa1 delta NT, by deleting the nitroxyl-terminal region of the Hpa1 sequence and compared Hpa1 delta NT with the full-length protein in terms of the effects on vegetative growth and related physiological responses in Arabidopsis. When Hpa1 was applied to plants, it acted to enhance the vegetative growth but did not affect the floral development. Enhanced plant growth was accompanied by induced expression of growth-promoting genes in plant leaves. The growth-promoting activity of Hpa1 was further correlated with a physiological consequence shown as promoted leaf photosynthesis as a result of facilitated CO2 conduction through leaf stomata and mesophyll cells. On the contrary, plant growth, growth-promoting gene expression, and the physiological consequence changed little in response to the Hpa1 delta NT treatment. These analyses suggest that Hpa1 requires the nitroxyl-terminus to facilitate CO2 transport inside leaf cells and promote leaf photosynthesis and vegetative growth of the plant.
Hpa1 是由水稻重要细菌病原体稻黄单胞菌产生的一种海因蛋白，具有促进植物生长的活性。为了了解 Hpa1 功能的分子基础，我们通过删除 Hpa1 序列的硝酰基末端区域生成了无活性的变异蛋白 Hpa1ΔNT，并比较了 Hpa1ΔNT 与全长蛋白在拟南芥营养生长和相关生理反应方面的影响。当 Hpa1 被应用于植物时，它可以促进营养生长，但不会影响花的发育。增强的植物生长伴随着植物叶片中促进生长基因的诱导表达。Hpa1 的促生长活性与一个生理后果相关联，表现为通过促进叶片气孔和叶肉细胞的 CO2 传导来促进叶片光合作用。相反，植物生长、促进生长基因表达和生理后果对 Hpa1ΔNT 处理的反应变化很小。这些分析表明，Hpa1 需要硝酰基末端来促进叶片细胞内的 CO2 运输，从而促进叶片光合作用和植物的营养生长。
