Soybean proteins GmTic110 and GmPsbP are crucial for chloroplast development and function

Abstract

We have identified a viable-yellow and a lethal-yellow chlorophyll-deficient mutant in soybean. Segregation patterns suggested single-gene recessive inheritance for each mutant. The viable- and lethal-yellow plants showed significant reduction of chlorophyll a and b. Photochemical energy conversion efficiency and photochemical reflectance index were reduced in the viable-yellow plants relative to the wildtype, whereas the lethal-yellow plants showed no electron transport activity. The viable-yellow plants displayed reduced thylakoid stacking, while the lethal-yellow plants exhibited failure of proplastid differentiation into normal chloroplasts with grana. Genetic analysis revealed recessive epistatic interaction between the viable- and the lethal-yellow genes. The viable-yellow gene was mapped to a 58kb region on chromosome 2 that contained seven predicted genes. A frame shift mutation, due to a single base deletion in Glyma.02g233700, resulted in an early stop codon. Glyma.02g233700 encodes a translocon in the inner membrane of chloroplast (GmTic110) that plays a critical role in plastid biogenesis. The lethal-yellow gene was mapped to an 83kb region on chromosome 3 that contained 13 predicted genes. Based on the annotated functions, we sequenced three potential candidate genes. A single base insertion in the second exon of Glyma.03G230300 resulted in a truncated protein. Glyma.03G230300 encodes for GmPsbP, an extrinsic protein of Photosystem II that is critical for oxygen evolution during photosynthesis. GmTic110 and GmPsbP displayed highly reduced expression in the viable- and lethal-yellow mutants, respectively. The yellow phenotypes in the viable- and lethal-yellow mutants were due to the loss of function of GmTic110 or GmPsbP resulting in photooxidative stress.

Transcriptome and proteomic analyses reveal multiple differences associated with chloroplast development in the spaceflight-induced wheat albino mutant mta

“…Chl is distributed in chloroplast thylakoid membrane and, as the main part of light harvesting complex, plays an important role in photosynthesis [9]. The Chl biosynthetic pathway and Chl metabolism have been extensively studied.…”

Genetics and Physiology of the Nuclearly Inherited Yellow Foliar Mutants in Soybean

“…Chlorophyll deficient mutants are broadly classified into two groups, viable-yellows and lethal-yellows. Viable-yellow mutant plants are capable of surviving with pale green or yellow/green leaves ( Palmer et al, 2000 ; Sandhu et al, 2016 ) ( Figure 1 ). As the seedlings grow, the plant may either outgrow the yellow leaves or retain the phenotype for the duration of its life depending on the mutated gene.…”

“…Lethal-yellow mutant seedlings are initially yellow colored and have stunted growth, but are incapable of surviving. The plants vary in their length of survival from only for a few days after germination to a few weeks ( Palmer et al, 2000 ; Sandhu et al, 2016 ).…”

“…The CD-5 and y11 mutants that exhibited similar phenotypes had identical amino acid substitution in paralogous genes ( Campbell et al, 2015 ). Y11, Y18/Y18_1, Y18_2, YL_PR350, PsbP , and CD-5 were genetically mapped to chromosomes 13, 14, 17, 15, 3 and 15, respectively ( Mahama et al, 2002 ; Kato and Palmer, 2004 ; Reed et al, 2014 ; Campbell et al, 2015 ; Sandhu et al, 2016 ).…”

“…In soybean, the majority of mutants cause a 30–66% reduction in overall chlorophyll content ( Shoemaker et al, 1985 ; Zhang et al, 2011 ; Sandhu et al, 2016 ). Lethal-yellow mutants have considerably higher reduction in chlorophyll content as compared to viable-yellow mutants.…”