Wickramanayake Janithri S, Goss Josue A, Zou Min, Goggin Fiona L
Department of Entomology and Plant Pathology, University of Arkansas, Fayetteville, AR, United States.
Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR, United States.
Front Plant Sci. 2020 Jun 26;11:932. doi: 10.3389/fpls.2020.00932. eCollection 2020.
Fatty Acid Desaturase 7 (FAD7) generates polyunsaturated fatty acids, promoting the desaturation of chloroplast membranes; it also provides an essential precursor for the synthesis of jasmonic acid (JA), a phytohormone that can influence plant growth, development, and primary metabolism. This study examined the effects of , a null mutation in , on the growth, morphology, and photosynthetic traits of tomato, . Although the mutant had a lower density of stomata than wild type plants, the two genotypes had comparable stomatal conductance, transpiration rates, and intracellular CO levels; in addition, had significantly thinner leaf blades, which may help maintain normal levels of CO diffusion despite the lower number of stomata. Surprisingly, also had significantly higher carbon assimilation (A) and maximum quantum efficiency of PSII (F/F) than wild type plants at both of the light intensities tested here (220 or 440 µmol m s), despite having lower levels of chlorophyll than wild type plants under low light (220 µmol m s). Furthermore, CO response curves indicated higher Rubisco activity (V) in compared to wild type plants, as well as an enhanced maximum rate of electron transport used in the regeneration of ribulose-1,5-bisphosphate (J). These data indicate that loss of function of FAD7 can enhance the efficiency of both light-dependent and light-independent reactions in photosynthesis. Consistent with this, the mutant also displayed enhanced growth, with significantly more leaves and a more compact growth habit. In contrast to , another tomato mutant impaired in JA synthesis () showed no enhancements in growth or photosynthetic efficiency, suggesting that the enhancements observed in are independent of the effects of this mutation on JA synthesis. These data demonstrate that loss of function of FAD7 can enhance photosynthesis and growth, potentially through its impacts on the chloroplast membranes.
脂肪酸去饱和酶7（FAD7）可生成多不饱和脂肪酸，促进叶绿体膜的去饱和；它还为茉莉酸（JA）的合成提供了一种必需的前体，茉莉酸是一种可影响植物生长、发育和初级代谢的植物激素。本研究检测了FAD7基因的无效突变对番茄（Solanum lycopersicum）生长、形态和光合特性的影响。尽管FAD7突变体的气孔密度低于野生型植株，但两种基因型的气孔导度、蒸腾速率和细胞内CO₂水平相当；此外，FAD7突变体的叶片显著更薄，这可能有助于在气孔数量较少的情况下维持正常的CO₂扩散水平。令人惊讶的是，尽管在低光强（220 μmol m⁻² s⁻¹）下FAD7突变体的叶绿素水平低于野生型植株，但在此处测试的两种光强（220或440 μmol m⁻² s⁻¹）下，FAD7突变体的碳同化（A）和PSII的最大量子效率（Fv/Fm）也显著高于野生型植株。此外，CO₂响应曲线表明，与野生型植株相比，FAD7突变体中核酮糖-1,5-二磷酸羧化酶（Rubisco）活性（Vₛₘₐₓ）更高，以及用于再生核酮糖-1,5-二磷酸的电子传递最大速率（Jₘₐₓ）增强。这些数据表明，FAD7功能丧失可提高光合作用中光反应和暗反应的效率。与此一致的是，FAD7突变体还表现出生长增强，叶片显著更多且生长习性更紧凑。与FAD7突变体不同，另一个JA合成受损的番茄突变体（spr2）在生长或光合效率方面没有增强，这表明在FAD7突变体中观察到的增强与该突变对JA合成的影响无关。这些数据表明，FAD7功能丧失可能通过其对叶绿体膜的影响来增强光合作用和生长。
