مقاله انگلیسی رایگان در مورد فتوسنتز تقویت شده در ریشه های رشادی – اسپرینگر 2018

In seed plants, plastids differentiate into various forms with their respective functions to fulfill the diverse roles of host cells (Jarvis and López-Juez 2013). Development of chloroplasts from other plastids, such as proplastids and etioplasts, is one of the most important cellular processes for plants to establish photoautotrophic growth. Photosynthesis allows plants to grow depending on light energy but with simultaneous threat of photooxidative damage to cells. Therefore, plants should strictly regulate development and the functionality of chloroplasts in coordination with the developmental and functional states of cells and tissues and in response to growth environments. However, the coordination mechanisms of cellular and plastid development remain largely elusive. In general, roots develop underground as heterotrophic organs with dependence on leaves for their energy and carbon source. In Arabidopsis thaliana, chloroplast development in roots is strongly suppressed in part via the auxin-signaling pathway, even when the roots are fully illuminated on transparent agar plates (Kobayashi et al. 2012). Chlorophyll (Chl) only slightly accumulates in illuminated Arabidopsis roots, particularly around the root–hypocotyl junction. Illuminated roots can perform photosynthetic electron transport but with lower photochemical efficiency and larger photoprotective nonphotochemical quenching (NPQ) than leaves (Kobayashi et al. 2013). GOLDEN 2-LIKE transcription factors in Arabidopsis (GLK1 and GLK2) positively regulate the expression of nuclear-encoded genes associated with Chl biosynthesis and light harvesting by binding directly to their promoter regions (Waters et al. 2009). We reported that overexpression of GLK1 and GLK2 (GLK1ox and GLK2ox) induced chloroplast development in roots (Kobayashi et al. 2012). However, the overexpression mainly increased light-harvesting complex (LHC) proteins and antenna pigments in roots, with enhanced grana stacking of the thylakoid membrane but no improvement in photosynthetic efficiency (Kobayashi et al. 2013). We recently revealed that shoot removal promotes chloroplast development in Arabidopsis roots, with improved photosynthetic efficiency, via a woundsignaling pathway (Kobayashi et al. 2017). In response to shoot removal, WOUND INDUCED DEDIFFERENTIATION (WIND) transcription factors, which are induced at the wound site, activate cytokinin signaling mediated by type-B ARABIDOPSIS RESPONSE REGULATORs (ARRs) in roots. Double knockout mutation of the major type-B ARRs, ARR1 and ARR12 (Mason et al. 2005), blocked photosynthetic remodeling, and Chl accumulation in roots after shoot removal (Kobayashi et al. 2017), so these factors are indispensable for the root greening response. Downstream of type-B ARRs, class B GATA transcription factors (B-GATAs), including GATA, NITRATE-INDUCIBLE, CARBON METABOLISM INVOLVED (GNC), and GNC-LIKE/CYTOKININRESPONSIVE GATA TRANSCRIPTION FACTOR 1 (GNL/CGA1) (Behringer and Schwechheimer 2015), may play an important role in chloroplast development in roots (Chiang et al. 2012, Kobayashi et al. 2017).