The Reason for Growth Inhibition of Ulmus pumila ‘Jinye’: Lower Resistance and Abnormal Development of Chloroplasts Slow Down the Accumulation of Energy

Abstract

Ulmus pumila ‘Jinye’, the colorful leaf mutant of Ulmus pumila L., is widely used in landscaping. In common with most leaf color mutants, U. pumila ‘Jinye’ exhibits growth inhibition. In this study, U. pumila L. and U. pumila ‘Jinye’ were used to elucidate the reasons for growth inhibition at the physiological, cellular microstructural, and transcriptional levels. The results showed that the pigment (chlorophyll a, chlorophyll b, and carotenoids) content of U. pumila L. was higher than that of U. pumila ‘Jinye’, whereas U. pumila ‘Jinye’ had a higher proportion of carotenoids, which may be the cause of the yellow leaves. Examination of the cell microstructure and RNA sequencing analysis showed that the leaf color and growth inhibition were mainly due to the following reasons: first, there were differences in the structure of the thylakoid grana layer. U. pumila L. has a normal chloroplast structure and clear thylakoid grana slice layer structure, with ordered and compact thylakoids. However, U. pumila ‘Jinye’ exhibited the grana lamella stacking failures and fewer thylakoid grana slice layers. As the pigment carrier and the key location for photosynthesis, the close stacking of thylakoid grana could combine more chlorophyll and promote efficient electron transfer promoting the photosynthesis reaction. In addition, U. pumila ‘Jinye’ had a lower capacity for light energy absorption, transformation, and transportation, carbon dioxide (CO2) fixation, lipopolysaccharide biosynthesis, auxin synthesis, and protein transport. The genes related to respiration and starch consumption were higher than those of U. pumila L., which indicated less energy accumulation caused the growth inhibition of U. pumila ‘Jinye’. Finally, compared with U. pumila ‘Jinye’, the transcription of genes related to stress resistance all showed an upward trend in U. pumila L. That is to say, U. pumila L. had a greater ability to resist adversity, which could maintain the stability of the intracellular environment and maintain normal progress of physiological metabolism. However, U. pumila ‘Jinye’ was more susceptible to changes in the external environment, which affected normal physiological metabolism. This study provides evidence for the main cause of growth inhibition in U. pumila ‘Jinye’, information for future cultivation, and information on the mutation mechanism for the breeding of colored leaf trees.

iTRAQ-Based Proteomic Analysis Reveals the Role of the Biological Control Agent, Sinorhizobium fredii Strain Sneb183, in Enhancing Soybean Resistance Against the Soybean Cyst Nematode

“…Trans-cinnamate 4-monooxygenase that is also called as cinnamate 4-hydroxylase (C4H) participates in the synthesis of numerous polyphenoid compounds by plants when challenged by pathogens, such as flavones, isoflavonoids, and lignin (Zhu et al, 2020). The accumulation of the enzyme in our study could be related to the accumulation of flavones and isoflavonoids, increasing lignification of the cell wall and then enhance soybean resistance, which is similar to the results in Ulmus pumila (Zuo et al, 2019). Moreover, increased expression levels of seven CHS were identified in present study.…”

Characterization and RNA-Seq Analysis of Yellow-Green Leaf Mutants in Tomato

“…Similarly, in the present study, a dark green leaf (GL) mutant with more developed and more closely arranged palisade tissue than normal leaf-color plants was reported. In general, thylakoids are carriers of pigments in plant leaves, and the accumulation of pigments is directly influenced by the stacking state of thylakoid layers [16]. Consistently, we also found that the lamellae were clear and that the stroma and grana were orderly, with more stacking and larger starch grains, as determined by observing the ultrastructure of the chloroplasts in GL leaves.…”

Molecular Mechanisms of Chlorophyll Deficiency in Ilex × attenuata ‘Sunny Foster’ Mutant

“…Therefore, the reduction in Chl content and the occurrence of aberrant structural alterations in chloroplasts should be the primary factors contributing to our study's observed decrease in photosynthetic capacity. Comparable findings were observed in the yellow mutant of U. pumila [38]. As a consequence of compromised photosynthesis, mutant leaves also exhibit deficiencies in carbon skeletons and major carbon metabolism end-products, including flavonoids, leading to delayed plant growth [59].…”

“…Due to impaired photosynthesis, the yellow NAU31 mutant had impaired chloroplast structure and reduced Chl and Car content [35]. Although, in recent years, ornamental plants have also witnessed the emergence of Chl-deficiency mutants, including species like G. biloba [36], Quercus shumardii [37], Ulmus pumila [38], Lagerstroemia indica [39], and Acer palmatum [40]. However, there is a paucity of comprehensive investigations into the molecular mechanisms underlying ornamental leaf color mutants.…”