The ZmMYB84‐ZmPKSB regulatory module controls male fertility through modulating anther cuticle—pollen exine trade‐off in maize anthers. Issue 12 (7th September 2022)

• Record Type: Journal Article
• Authors: Liu, Xinze; Jiang, Yilin; Wu, Suowei; Wang, Jing; Fang, Chaowei; Zhang, Shaowei; Xie, Rongrong; Zhao, Lina; An, Xueli; Wan, Xiangyuan
• Is Part Of: Plant biotechnology journal. Volume 20:Issue 12(2022)
• Page Start: 2342
• Page End: 2356
• Publication Date: 2022-09-07
• Subjects: ZmMYB84‐ZmPKSB regulatory module -- polyketide synthase -- lipid metabolism -- trade‐off -- anther cuticle -- pollen exine; Plant biotechnology -- Periodicals; Plant genetic engineering -- Periodicals; 630.272
• DOI: 10.1111/pbi.13911
• Languages: English
• ISSNs: 1467-7644

Abstract

Summary: Anther cuticle and pollen exine are two crucial lipid layers that ensure normal pollen development and pollen–stigma interaction for successful fertilization and seed production in plants. Their formation processes share certain common pathways of lipid biosynthesis and transport across four anther wall layers. However, molecular mechanism underlying a trade‐off of lipid‐metabolic products to promote the proper formation of the two lipid layers remains elusive. Here, we identified and characterized a maize male‐sterility mutant pksb, which displayed denser anther cuticle but thinner pollen exine as well as delayed tapetal degeneration compared with its wild type. Based on map‐based cloning and CRISPR/Cas9 mutagenesis, we found that the causal gene ( ZmPKSB ) of pksb mutant encoded an endoplasmic reticulum (ER)‐localized polyketide synthase (PKS) with catalytic activities to malonyl‐CoA and midchain‐fatty acyl‐CoA to generate triketide and tetraketide α‐pyrone. A conserved catalytic triad (C171, H320 and N353) was essential for its enzymatic activity. ZmPKSB was specifically expressed in maize anthers from stages S8b to S9‐10 with its peak at S9 and was directly activated by a transcription factor ZmMYB84. Moreover, loss function of ZmMYB84 resulted in denser anther cuticle but thinner pollen exine similar to the pksb mutant. The ZmMYB84‐ ZmPKSB regulatory module controlled a trade‐off between anther cuticle and pollen exine formation by altering expression of a series of genes related to biosynthesis and transport of sporopollenin, cutin and wax. These findings provide new insights into the fine‐tuning regulation of lipid‐metabolic balance to precisely promote anther cuticle and pollen exine formation in plants. Abstract : Maize male‐sterility mutant pksb displays dense anther cuticle but thin pollen exine. ZmPKSB has conserved polyketide synthase activities dependent on a catalytic triad (C171, H320 and N353). ZmPKSB is directly activated by a transcription factor ZmMYB84, thus forming a regulatory module (ZmMYB84‐ ZmPKSB ) that plays synchronous roles in anther cuticle and pollen exine formation required for male fertility. The ZmMYB84‐ ZmPKSB regulatory module controls a trade‐off of lipid‐metabolic products individually used for anther cuticle and pollen exine formation.