Comprehensive transcriptome analysis of phytohormone biosynthesis and signaling genes in rice microspore/pollen and tapetum

Abstract

To investigate the involvement of phytohormones during rice microspore/pollen (MS/POL) development, endogenous levels of several phytohormones in the mature anther were analyzed. We also analyzed the global expression profiles of genes related to seven phytohormones: auxin, gibberellins (GAs), cytokinins (CKs), brassinosteroids, ethylene, ABA, and jasmonic acids, in MS/POL and tapetum (TAP) using a 44K microarray combined with a laser-microdissection technique (LM-array analysis). IAA and GA₄ accumulated at an extremely higher amount in the mature anther compared to the other tissues and organs, while CKs and ABA did not. LM-array analysis revealed that sets of genes required for IAA and GA synthesis were expressed coordinately during the later stages of MS/POL development. In contrast, genes for GA signaling were preferentially expressed during the early developmental stages of MS/POL and throughout TAP development, while their expression was clearly down-regulated at the later stages of MS/POL development.