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Mengyang Liu, Yin Lu, Shan Wang, Fang Wu, Jingrui Li, Yanhua Wang, Jianjun Zhao, and Shuxing Shen

Leaf color mutants play an important role in our understanding of chlorophyll biosynthesis and catabolism. In this study, we obtained a yellow-green leaf mutant hy in an ethyl methanesulfonate mutagenized population of chinese cabbage (Brassica rapa ssp. pekinensis). The hy phenotype was controlled by a recessive allele at a single locus. The intrinsic photochemical activity of photosystem II (PSII) is impaired in hy, suggesting that absorbed light energy is not efficiently transferred from the light-harvesting complexes antenna to the PSII reaction centers and dissipated as heat or fluorescence. We measured chlorophyll content and chlorophyll precursors and analyzed the expression of key genes in the chlorophyll synthetic pathway in hy and wild type. The mutation phenotype was consistent with inhibited expression of chlorophyll a oxygenase (CAO) gene in the chlorophyll synthetic pathway. In mutant hy, CAO cDNA was cloned so that a C to T mutation at 1099 bp caused a conserved proline (Pro) to serine (Ser) mutation at the 367th amino acid in C-domain, which changed the secondary structure of CAO protein. We speculate that the mutation amino acid changed in the C-domain may affect the catalytic function in mutant CAO.

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Sheng Chen, Zhenchang Wang, Zhanyu Zhang, Xiangping Guo, Mengyang Wu, Ghulam Rasool, Rangjian Qiu, and Xiaojun Wang

Soil salinity influences plant growth and crop yield significantly. Former studies indicated that uneven salt distribution in the root zone could relieve salt stress. But, how uneven salt distribution influences Na+ and Ca2+ concentration in the stem, leaf, and fruit and whether this influence would bring effects on fruit blossom-end rot (BER) still needs to be further studied. Under consideration of this, pot experiment with four treatments, T1:1, T1:5, T2:4, and T3:3, was conducted by setting the upper soil layer salinity at 1‰, 1‰, 2‰, and 3‰ and the lower soil layer at salinities of 1‰, 5‰, 4‰, and 3‰, respectively. Compared with the uniform salt concentration in the root zone (T3:3 treatment), the incidence of BER in the T1:5 and T2:4 treatments decreased by 60% and 35%, respectively. The fruit Na+ concentration and Na+/Ca2+ ratio were positively correlated with the incidence of BER. The value of the upper-root selective absorption Ca2+ over Na+ (SCa/Na(upper root)) for T1:5 was 0.8 times more than that of T1:1. The results showed that the incidence of BER was positively correlated with root dry matter and SCa/Na(root) weighted mean salinity. The overall results suggested that uneven salt distribution in the root zone could promote the Ca2+ absorption, Ca2+/Na+ ratio, and selective absorption Ca2+ over Na+ and consequently decrease the incidence of BER in tomato fruit.