Effects and Mechanism of Enhanced UV-B Radiation on the Flag Leaf Angle of Rice

Abstract

Leaf angle is an influential agricultural trait that influences rice (Oryza sativa L.) plant type and yield, which results from the leaf bending from the vertical axis to the abaxial axis. UV-B radiation affects plant morphology, but the effects of varying UV-B intensities on rice flag leaves and the underlying molecular, cellular, and physiological mechanisms remain unknown. This experiment aims to examine the effect of natural light and field-enhanced UV-B radiation (2.5, 5.0, 7.5 kJ·m−2) on the leaf angle of the traditional rice variety Baijiaolaojing on Yuanyang terraces. In comparison with natural light, the content of brassinolide and gibberellin in rice flag leaves increased by 29.94% and 60.1%, respectively. The auxin content decreased by 17.3%. Compared with the natural light treatment, the cellulose content in the pulvini was reduced by 13.8% and hemicellulose content by 25.7% under 7.5 kJ·m−2 radiation intensity. The thick-walled cell area and vascular bundle area of the leaf pulvini decreased with increasing radiation intensity, and the growth of mechanical tissue in the rice leaf pulvini was inhibited. The flag leaf angle of rice was greatest at 7.5 kJ·m−2 radiation intensity, with an increase of 50.2%. There are two pathways by which the angle of rice flag leaves is controlled under high-intensity UV-B radiation. The leaf angle regulation genes OsBUL1, OsGSR1, and OsARF19 control hormone levels, whereas the ILA1 gene controls fiber levels. Therefore, as cellulose, hemicellulose, sclerenchyma, and vascular bundles weaken the mechanical support of the pulvini, the angle of the flag leaf increases.

WGCNA analysis of the effect of exogenous BR on leaf angle of maize mutant lpa1

“…The development of the plant leaf angle is affected by many factors, and hormones play an important regulatory role in the development of the leaf angle 30 , 31 . Therefore, the role of BR in the process of plant leaf angle development and growth is not negligible, and we found that there were 6 DEGs associated with the brassinosteroid biosynthesis pathway by KEGG analysis of DEGs of WT and lpa1 , and one of the genes encoding steroid 5α-reductase found that the oxidative stress resistance of arabidopsis DET2-deficient plants was enhanced, which may be due to physiological stress caused by long-term lack of BRs in plants.…”

Potential Role of Phytochromes A and B and Cryptochrome 1 in the Adaptation of Solanum lycopersicum to UV-B Radiation

“…Whereas chlorophyll a is found in the core complex of both photosystems (PSI and PSII), chlorophyll b is found in the PSII antenna system. Thus, an increase in the ratio of chlorophyll a/b shows a higher susceptibility of the complex to UV-B compared to the peripheral antenna complex [48]. Before UV-B irradiation, the chlorophyll ratio was slightly higher in the phyab2 and cry1 mutants (2.2-2.3) than in the WT (2.1).…”

The recent possible strategies for breeding ultraviolet-B-resistant crops

“…UVB radiation reduced the transcript levels of unidentified GA20-oxidase ( GA20ox ) and GA3-oxidase ( GA3ox ) family members involved in gibberellin biosynthesis [ 58 ]. Furthermore, gibberellin and brassinolide have been found to positively control the flag leaf angle under increased UVB radiation [ 59 ], possibly owing to an imbalance in cell division and growth on the adaxial and abaxial surfaces of the lamina [ 60 , 61 ]. The effects of UVB-induced growth inhibition maybe controlled by regulating the gibberellin signaling pathway, which control cell division and elongation.…”